This chapter also covers chromosomal errors such as nondisjunction, deletions, duplications, and inversion.
The inheritance of one trait does not affect the inheritance of another trait.
If two pure-breeding varieties are crossed, all offspring look like the parent.
The law of independent assortment does not apply to linked genes.
Down, Klinefelter, Turner syndromes are nondisjunction errors.
The premise is that offspring are more like their parents than less closely related individuals.
In this chapter, we discuss some terms that are important to your study of heredity.
Thomas Morgan's work on fruit flies paved the way for the discovery of linked genes, genetic recombination, and sex-linked inheritance.
The discussion ends with a look at linkage maps.
It is important to discuss the types of chromosomal errors that can occur during reproduction since chromosomes carry the vital genes necessary for proper development and passage of hereditary material from one generation to the next.
The improper separation of chromosomes during meiosis leads to an abnormal number of chromosomes in offspring.
The chapter ends with an examination of the other major types of chromosomal errors.
Two alleles for fur color could be B and b.
The first generation of offspring, or the first filial generation in a genetic cross.
The second generation of offspring is called the filial generation.
A simple example of this would be fur color where B represents brown and b represents black.
There are three possible genotypes: brown, Bb, and black.
Down, Turner, and Klinefelter syndromes are some of the classic examples of nondisjunction-related syndromes.
Some of the characteristics of the peas were round, wrinkled, green, yellow, purple, and white.
The person with the most associated name with heredity is Gregor Mendel.
He worked with peas for many years.
It was a strange hobby, but it was useful to the world of science.
He recorded the results of theploidy of peas in order to figure out how certain characters are born.
A blue flower mixed with a yellow flower will produce a green flower.
The genes of each parent would always be the same as the blended colors.
The law of segregation and the law of independent assortment are the two fundamental theories developed by Mendel.
There is a single character in which both parents are Heterozygous.
A 3:1 phenotype ratio is given by a mono hybrid cross between gametes.
Multiple characters were also experimented with by Mendel.
The offspring have a 9:3:3:1 phenotype ratio.
The law of segregation and the law of independent assortment were developed from his experiments.
If an individual is Bb for eye color, during gamete formation, one gamete would receive a B and the other would receive a b.
When the gametes are formed, members of each pair of factors are distributed.
Heredity 101 does not affect the inheritance of another trait.
If an individual is BbRr for two genes, gametes could contain br, bR, or br.
When two pure-breeding varieties are crossed, all the offspring look like one parent.
Look at the organisms and determine if they are tall or short, have blue or brown eyes, and so on.
The geno is known in the case of a trait.
If a person has blue eyes, it's the genotype.
If the person has brown eyes, you can't be sure if the person has a dominant or submissive genotype.
Geneticists breed the organisms whose genes are unknown with the ones that have the trait.
This results in offspring with observable characteristics.
The experiments are not done on humans.
There are many statistical laws of heredity.
A Yy x Yy cross will result in a 3:1 ratio of the dominant trait to the mono hybrid.
A di hybrid cross, such as YyRr x YyRr, will result in a ratio of 9:3:3:1, according to him.
Mono- and di hybrid crosses are implied by the two ratios that appear in genetic analysis problems.
Mendel's pea experiments seem to indicate that the inheritance of traits is not always simple.
It's not always a dominant or a swerving trait that is 9:3:3:1 or 3:1.
The parents' genetic input is mixed with the phenotype.
One example of incomplete dominance is the flower color of a snapdragon plant, which can be red, white, or pink.
Children as young as two years old can be at risk for heart attacks because of a disorder that causes cholesterol levels to be many times higher than normal.
Those who are HH tend to have normal cholesterol levels, while those who are Hh tend to have high cholesterol levels.
The environment is a major factor in how genetic conditions express themselves.
If a person has poor diet or exercise habits, they don't necessarily have normal cholesterol levels.
The former is a name for incomplete dominance, whereas the former was a theory on heredity.
The "hypothesis" says that the HH and hh extremes can't be retrieved.
Blending inheritance says that if you were to cross two Hh individuals, the offspring could still be HH or hh.
The human blood groups M, N, and MN are examples of codominance.
Both alleles are codominant and this is not incomplete dominance.
A polygenic trait is eye color.
Different genes determine each of these characteristics.
Skin color is determined by at least three different genes working together to produce a wide range of possible skin tones.
There are many monogenic traits that correspond to two alleles, one dominant and one recessive.
More than two alleles are involved in other traits.
The human blood type is a classic example of this trait.
There are four major blood types: A, B,AB, and O.
They are named because of the presence or absence of certain antigens on the red blood cells.
The possible blood types for humans are IAi, IAIA, I Bi, IBIB, and IA IB.
The A and B all genes appear on the surface of the red blood cell, as we saw in the MN blood groups.
The dominance of IA and IB over i is a classic example of how complex blood type analysis can be.
People with type A blood produce anti-B antibodies because the B antigen that is present on type B and typeAB blood is a foreign molecule to someone with type A blood.
The body's defense mechanism is doing its job.
The universal acceptor of blood is people who are typeAB.
If you give type B blood to a person with type A blood, the recipient will have an immune response to the transfused blood.
The surface of red blood cells have no antigen on them.
People with type O blood are universal donors because they don't have an adverse reaction to the blood.
Chapter 15 of Human Physiology talks about immune reactions.
The coat color of mice is a classic example of epistasis.
Black is the dominant color over brown.
The coat color gene is not the only one that controls the deposition of pigment in the fur.
If a mouse has a dominant allele of the Cc or CC, it leads to deposition and the coloring of the fur according to the coat color gene's instructions.
If a mouse has this trait, it will have white fur no matter what the coat color is, because it won't put anything into the fur.
It's almost as if the coat color genes were overruled.
If you mate two black mice that are BbCc, the ratio of the offspring's phenotypes would not be the 9:3:3:1 ratio that Mendel predicts, but rather 9:4:3 black:white:brown.
A good example of pleiotropy is the cause of sickle cell anemia.
The blood cells are "sucked" by this single gene, which leads to symptoms such as heart, lung, and kidneys damage, weakness, and generalized fatigue.
There are many problems that can lead to disastrous side effects.
The system as a whole is affected by a single gene.
There were other people who made progress in the field of heredity.
Sex linkage and linked genes were discovered by Thomas Morgan.
The sex chromosomes, X and Y, are the most important parts of the human cell.
Women have the same X chromosomes.
Men have one X and one Y.
A fruit fly species was tried on by Morgan.
There were four pairs of chromosomes in the fruit flies.
Morgan crossed a white-eyed male with a red-eyed female and all the F1 offspring had red eyes.
He obtained a 3:1 ratio when he bred the F1 together.
The white trait was restricted to males, which was a slight difference from what Mendel's theories would predict.
Morgan found that the eye color genes are on the X chromosomes.
The poor male flies only get a single copy and if it is abnormal, they are abnormal.
Even if one copy is not, the lucky ladies are still normal.
Sex-linked conditions are possible because of the male-female sex chromosomes difference.
A male needs only one of the two faulty versions of the gene to show the disease.
Sex-linked traits can be explained by the fact that males don't have a corresponding gene on the Y chromosome to counter the negative effect of a X chromosome allele.
The father is not involved in the passage of an X-linked gene to the male children of a couple.
fathers don't pass alleles to their sons The father doesn't give an X chromosomes to the male offspring because he is the one who gives the Y chromosomes.
Individuals with this condition have difficulty with blood clotting.
After the smallest of injuries, those most severely affected by the disease can die.
This condition is found mostly in males.
Only the active X chromosomes are expressed by a cell.
Random inactivation of one of the female's X chromosomes occurs in each cell.
Some cells inactivate the same X.
Different cells will have different X chromosomes.
Sometimes they do, but usually they have enough cells with a good copy of the allele to compensate.
Ear hair distribution is a holandric trait in humans.
Each chromosome has hundreds of genes that are passed along as a unit.
The law of independent assortment does not apply to linked genes.
Morgan looked at body color and wing size on his fruit flies.
G and V were the dominant alleles, with the other two being black and v. GgVv females were crossed with ggvv males.
The law of independent assortment predicts the offspring of four different things.
That is not what Morgan found.
The gray/normal flies only produce gv gametes because the genes are linked.
Morgan expected the ratio of offspring to be half GgVv and half gg.
Morgan found that there were more flies than the independent assortment would have you believe.
The closer the genes are to the chromosome, the less this occurs.
The farther apart the two genes are, the more often they will intersect.
The creation of linkage maps can be used to determine how close two genes are to each other.
One map unit is equal to 1 percent.
You know that A crosses over with C 20 percent of the time, B crosses over with C 15 percent of the time, and A crosses over with D 10 percent of the time.
You can determine the sequence from this information.
Gene B could be 5 or 35 units from A.
If you know that A is 10 units from D and D is 5 units from B, you can determine that B must be 5 units from A as well.
This is a little harder than the others.
The first time you toss the coin, there is a chance that it will land on heads or tails.
It has a chance of landing heads and tails when you toss it again.
In the figure, focus on the tosses that land heads.
1 and 2 of them will land heads the second time.
The chance of getting heads twice with two coin tosses is 1 / 4.
To determine the probability that two random events will occur in succession, you simply divide the probability of the first event by the probability of the second event.
We follow the same thought process to understand the law of segregation.
You can get 1 / 4 by using 1 / 2 and 1 / 2.
It is important to understand the probability concept.
Squares and circles are used for males and females.
Below their parents are their offspring.
A shaded individual is being studied.
If the condition being studied is a monogenic recessive condition, the shaded gray have the genotypic rr.
A line through a symbol shows that the person is dead.
There are many ways in which pedicures can be used.
Two people want to have a child, and they both have a family history of a certain condition.
We can determine the father's probability of being a carrier.
We know that both of his parents have a Dd.
We build a Punnett square for a mono hybrid cross of the father's parents.
He would have the condition if we knew that he was not dd.
There are two "carrier" genotypes that are likely to be used for the father.
The probability of him being a carrier is 2.
We don't need a Punnett square to figure it out.
Her mother died of the condition, which means that she must have passed along a d to each of her children.
The mother in question does not have the condition, so she must have a D as well.
We need to determine the probability that one of their offspring will have the condition now that we know that they are both carriers.
The law of multiplication shows that the probability of this couple having a child with the condition is 2 / 3 x 1 x 4.
If they had a child with the condition, we would know that they are a carrier.
Some of the most common examples are Tay-Sachs disease, cystic fibrosis, and phenylketonuria.
These diseases can be used as examples on the AP Biology exam and can also help you in writing a well-supported essay answer to a question about heredity and inherited disorders.
The carriers of this disease do not show any effects of the disease and thus the allele is preserved in the population.
There is a higher than normal percentage of people with this disease.
There is a gene on the 7th.
The normal allele is involved in cellular ion transport.
The mucus accumulates in the lungs and digestive tract because of a faulty version of this gene.
Children with the disease die at a very young age.
One in 25 Caucasians is a carrier for this disease.
It results in a less efficient form of hemoglobin.
When the oxygen content of the blood is low, it can cause pain, muscle weakness, and fatigue.
African Americans are more likely to be affected by the most common inherited disease.
One out of 10 African Americans is a carrier of the disease.
The trait is so prevalent because carriers have increased resistance to Malaria.
The presence of the trait in the population increases due to the fact that it increases an individual's probability of survival.
Children with PKU can't digest phenylalanine.
Mental retardation can be caused by a by-product in the blood.
If the disease is caught early, the retardation can be prevented.
Humans are less likely to have dominant disorders.
It doesn't show itself until a person is in their 30s or 40s, and people with this condition have a 50 percent chance of passing it on to their offspring.
Think about how genes are passed down from generation to generation.
An individual can be a carrier of a condition without even knowing it.
It is not possible to be unaffected by a dominant condition and many lethal conditions have killed the individual before reproductive maturity has been achieved.
It is more difficult for the dominant genes to be passed along.
A dominant disorder must not kill an individual until reproduction occurs.
We've spent a lot of time talking about how genes are passed from generation to generation.
It is important to discuss situations in which something goes wrong with the chromosomes that affect the inheritance of genes by the offspring.
During meiosis I or II, it can happen.
The result is that one gamete gets too many of one kind of chromosomes, and another gamete gets none.
People with trisomy 21 can be provided with most orders.
It is rare for a baby to survive for more than a year with either of these conditions.
There are syndromes with aneuploidy of the sex chromosomes.
There is an extra Y chromosome for males.
Although this nondisjunction does not seem to produce a major syndrome, XYY males tend to be taller than average, and some geneticists believe they display a higher degree of aggressive behavior.
These individuals have male sex organs but are infertile.
Females also experience nondisjunction as well.
There is no real syndrome for females who are XXX.
The sex organs of sterile females fail to mature at puberty.
There are other types of chromosomal abnormality that can lead to diseases.
A small head, mental retardation, and abnormal facial features are caused by this syndrome.
Most affected individuals die young.
A piece of chromosomes 9 has been swapped with a piece of chromosomes 22 in this disease.
If this occurs in the middle of a sequence, it can render a gene nonfunctional.
There are serious effects on an organisms.
The AP Biology exam writers want you to be familiar with the major concepts of heredity.
Keep in mind the laws of probability when you try the practice problems that follow.
In squirrels, gray color is domi B.
There is a black squirrel.
A court case is trying to determine if the offspring will display a particular baby.
There are questions about D. O and A condition.
What is the chance of their second A.
Imagine tulips are either yellow or white.
The parents of C. Turner syndrome must be yellow.
There is a syndrome called E.Edwards syndrome A.
They produced only pink snapdragons with 200 white snapdragons.
The offspring of the two pink snapdragons would most likely be A.
You know the individual of the distance between the different genes on a has the Gg if you look at the crossover frequencies.
The Punnett square shows all during the first phase of meiosis.
The possible gamete combinations from this cross are first told to you.
A way to deter on a map.
We can tell you that AABbCc can have 22 gametes of 15 percent for B and C. The map shows that they are 15 units apart.
Person A must have a certain genetic makeup because he is on.
Some children have the same genes as Gene A and C. This means that some of the genes must be present.
His wife is between A and B.
Gene A crosses over with D 10 percent and the second b to the child who does not have the condition, if the father contributes B A (20) C (15) B A (10) D D (25) B to the child who does not have the condition.
Person B is most likely carrying a genetic abnormality.
It is closer to A than it is to B.
You can know that he is either a boy or girl.
If it used this knowledge to eliminate answer choices were B and C.
Gene A crosses over with E and it leads you to believe that he is most likely percent.
You don't know which side of A genes.
B is not certain, but it is with B.
A is the correct answer because neither parent is on the question map.
This is a test.
The probability that each of them is Bb is determined by the geno.
There is a chance that person C is Bb.
If they don't have any offspring with the same genes, he can have two.
The person who does not have the condition is most likely GG.
One-half of the offspring have a chance that person D is Bb.
Her parents don't have the condition, but she has a brother who does.
The only colors that can be used for the condition are yellow and white of her parents.
If white were not domi.
Remaining if it were intermediate inheritance.
You probably wouldn't get a straight yellow probability of 2 / 3, or 0.67, if you gave her two of these three.
It is necessary to express fully.
If yellow were late in the game, you could produce a yellow child who is bb.
If there was a Y allele in one of the parents, that's what the Punnett square said.
The A cross of yy x yy would only produce a white probability that they will have a child with tulips.