Biology Exam 8-12

creation of genetically identical offspring by a sing parent (no eggs and sperm)

Produce offspring that are genetic copies of the parent and identical to each other (clones)

reproduction that requires the fusion of gametes (sperm and eggs)

proceeds daughter cells or gametes

cells originate only from preexisting cells

each species carries its own specific genetic information

• Cell division involves the separation of sister chromatids and results in two daughter cells, each containing a complete and identical set of chromosomes.

prokaryotic cells reproduce asexually, binary fission means dividing in half

In Prokaryotes, most genes are carries on one circular DNA molecule, with associated proteins constitutes the organisms SINGLE CHROMOSOME

• as the cell relocated the one chromosome

• the copies move apart

• the plasma membrane pieces inward and more cell wall is made, which divides the parent cell into two daughter cells

In Eukaryotes, there are many more genes than prokaryotic cell, and they are grouped into MULTIPLE CHROMOSOMES in the nucleus

• Each eukaryotic chromosome contains one long D N A molecule.

• Individual chromosomes are visible under a light microscope only when the cell is in the process of dividing; otherwise, chromosomes are thin, loosely packed chromatin fibers too small to be seen

interphase + mitotic phase (mitosis + cytokinesis)

Division of nucleus into two identical nuclei

Division of the cytoplasm immediately after mitosis

Contains identical DNA

• before cells start dividing, the chromosomes duplicate producing sister chromatids

• DNA after it has duplicated and has two identical copies (connected most closely at the centromere) The

DNA structures that carry a cell’s genetic information and are found in the nucleus of eukaryotic cells

DNA (and its associated proteins) in a diffuse, stretched-out form when a cell is not dividing and cannot be seen in a light microscope

is an ordered sequence of events that run from the time a cell is first formed from a dividing parent cell until its own division into two cells

cell grows, has high metabolic activity, synthesizes organelles, and performs its normal function. Includes G1 + S + G2 phases

growth and metabolism (DNA in chromatin form)

duplication/replication of DNA (still in chromatin form)

preparation for cell division (sister chromatids in chromatin form)

distributes duplicated chromosomes into two daughter nuclei (mitosis = division of nucleus)

made up of microtubules, moves the chromosomes to the middle of the cell

chromosomes condense and spindle forms

Double

nuclear membranes breaks down and microtubules reach each the chromosomes

• single

spindle complete and chromosome lines up in the middle

• Double

sister chromatids separate and move to opposite poles of the cell

• single

nuclear envelope forms, chromatin uncoils, cleavage furrow forms

• Double

In animals

• cytokinesis occurs when a cell constricts, forming a cleavage furrow

• Contracting microfilaments pinch the cell in two like a drawstring

In plants

• a membranous cell plate forms and then split the cell in two

• vesicles collect in the center and fuse

a protein that stimulates cells to divide

a disease of the cell cycle

• the cells divide excessively to form masses called tumors. They do not need cell cycles

the abnormal cells remain at the original site

the abnormal cells spread to nearby tissues and invade other parts of the body. This is cancer and the spread of cancer cells beyond the original site is metastasis

the division of a single diploid nucleus unto four haploid nuclei (gametes)

• The somatic (body) cells of each species contain a specific number of chromosomes; for example, human cells have 46, consisting of 23 pairs of homologous chromosomes - one inherited from your mother, one from your father

one inherited from your mother, one from your father

Cells with two sets of homologous chromosomes (46 chromosomes in humans (one from each parent)

eggs and sperm, are haploid cells with a single set of chromosomes (23 chromosomes)

chromosome duplication, but the cell DIVIDES TWICE to four four daughter cells (gametes)

homologous chromosomes exchange corresponding segments

the haploid cells with duplicated chromosomes

•separates the members of each homologous pair and produces two daughter cells, each with one set of chromosomes.

• starts with the pairing of homologous chromosomes

the sister chromatids separate and create four haploid cells

–Mitosis produces two genetically identical diploid somatic daughter cells.

–Meiosis produces four genetically unique haploid gametes.

• How are they similar

• Both mitosis and meiosis begin with diploid parent cells that have chromosomes duplicated during the previous interphase.

an exchange of corresponding segments between nonsister chromatids of homologous chromosomes

it is a Photographic inventory of an individual chromosomes

How do you prepare them?

•white blood cells are isolated, stimulated to grow, arrested at metaphase stained to reveal band patterns, and

photographed under a microscope

The chromosomes are arranged into ordered pairs so that any chromosomal abnormalities can be detected

•An abnormal chromosome count is the result of nondisjunction, which can result when members of a chromosome pair fail to separate during meiosis:

–the failure of a pair of homologous chromosomes to separate during meiosis I or

–the failure of sister chromatids to separate during meiosis I IWhic

Trisomy 21 results in Down syndrome

The copies fo chromosome 21 fail to separate during meiosis

Klinefelter Syndrome (male)- XXY

Turner Syndrome (female)- XO

Chromosome breakage can lead to rearrangements—deletions, duplications, inversions, and translocations—that can produce genetic disorders or, if the changes occur in somatic cells, cancer

He was the guy who studied the pea plant

•is the transmission of traits from one generation to the next.

–You inherit traits from your parents

• **(**the scientific study of heredity) began with Gregor Mendel’s experiments.

–A heritable feature that varies among individuals is called a character.

–Mendel crossed pea plants and traced traits(variants of a character) from generation to generation.

True-Breeding-

Hybrids- offspring of two different varieties

P generation- parent generation

F1 generation-first generation of offspring

F2 generation- offspring of F1 generation

alternative versions of gene that account for variations in inherited characters

An organism that has two identical alleles for a gene

an organism that had two different alleles for a gene

if the two alleles of an inherited pair differ (heterozygous) and one determines the organism’s appearance

one of the alleles has no noticeable effect on the organism’s appearance

A sperm or egg carries only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes (meiosis).G

the different variations in the punnet square

Ex: PP, Pp, Yg

Examples- BB; homozygous dominant

Bb; Heterozygous

bb; homozygous recessive

what it looks like

Ratio example- 3 purple : 1 white

a cross between two individuals that are heterozygous for one character

a cross between two organisms that are each heterozygous for two characters being followed

the alleles of a pair segregate independently of other allele pairs during gamete formation

it can reveal the unknown genotype, a mating between an individual of unknown genotype and a homozygous recessive individual,

a family tree of traits of parents and children across generations

we use this to deduce the genetic information, and can also determine individual genotypes

this phenotype in humans is controlled by three alleles that produce a total of four phenotypes

•Both alleles are expressed in heterozygous individuals (IAIB), who have type A B blood

occurs when one gene influences multiple characters

• is a human example of pleiotropy.

–This disease affects the type of hemoglobin produced and the shape of red blood cells, andcauses anemia and organ damage.

–Sickle-cell and nonsickle alleles are codominant.

–Carriers of sickle-cell disease have increased resistance to malaria.

which a single phenotypic character results from the additive effects of two or more genes on a single phenotypic character

• ex; human height

–are located close together on the same chromosome and

–tend to be inherited together.

–These genes do not follow the Law of independent assortment

homologous chromosomes produces new combinations of alleles in gametes

•Linked genes can be separated by crossing over, forming recombinant gametes.

•The percentage of recombinant offspring among the total is the recombination frequency.

Males- XY

Female- XX

–The Y chromosome has genes for the development of testes, whereas an absence of the Y allows ovaries to develop.

•In humans, however, if this gene is not turned on, ovaries develop even in an XY embryo

•In humans, sex is determined by the interactions of several proteins produced by different genes, including autosomal (non-sex chromosome) genes.

–Because of this complexity we now know that sex in humans is not a binary state, and has many variations

a gene located on either sex chromosome

control trains unrelated to sex

–Red-green colorblindness

–Hemophilia – lack protein required for blood clotting

Must be homozygous for the allele

Albinism, Cystic Fibrosis, Phenylketonuria (P K U), Sickle-cell disease, Tay-Sachs disease

can be heterozygous because it is dominant

Achondroplasia, Huntington’s disease, Hypercholesterolemia

Watson and Crick-were the first to the finish line (their paper showing the model of DNA was published in 1953), their model gave new meaning to the words genes and chromosomes. The genetic information in a chromosome is encoded in the nucleotide sequence of D N A.

Rosalind Franklin- had taken an x-ray image of DNA and knew that the sugar-phosphate backbone was on the outside and the nitrogenous bases were on the inside

Hershey and Chase- able to show that certain bacteriophages (or phages, bacterial viruses) reprogram host cells to produce more phages by injecting their DNA

Chargaff-was a biochemist and had discovered that the amount of C in DNA equaled the amount of G

•D N A and R N A are nucleic acids consisting of long chains (polymers) of chemical units (monomers) called nucleotides.

• One of the two strands of D N A is a D N A polynucleotide, a nucleotide polymer (chain)

•A nucleotide is composed of a nitrogenous base, five-carbon sugar, and phosphate group.

•Each type of D N A nucleotide has a different nitrogen-containing base: adenine (A), cytosine (C), thymine(T), and guanine (G)

a sugar-phosphate backbone

Functional groups determine which two bases can form hydrogen bonds

DNA’s location in the nuclei of eukaryotic cells

–Is single stranded

–uses the sugar ribose (instead of deoxyribose in D N A) and

has a nitrogenous base uracil (U) instead of thymine

•starts with the separation of D N A strands.

•Enzymes then use each strand as a template to assemble new nucleotides into a complementary strand.

•requires the coordination of more than a dozen enzymes and other proteins

•DNA is untwisted and the two new strands are made roughly simultaneously

•Human cells have more than 6 billion base pairs but can replicate in a few hours

•Accurate - only about one nucleotide in several billion is mispaired

–The two D N A strands separate.

–Each strand then becomes a template for the assembly of a complementary strand from a supply of free nucleotides.

–Each new D N A helix has one old strand with one new strand (half of the parent molecule is conserved in each ‘daughter’ molecule).

the cell synthesizes one daughter strand as a continuous piece

The other strand is synthesized as a series of short pieces, which are then connected by this enzyme

•is the synthesis of R N A under the direction of DNA

is the synthesis of proteins under the direction of RNA

•is defined as a region of DNA that can be expressed to produce a functional product that is either a polypeptide or an R N A molecule.

–Recall that a polypeptide is a polymer of a protein

The genetic instructions for the amino acid sequence of a polypeptide chain are written in DNA and RNA as a series of non overlapping three-base “words” called codons.

AAACCGGCAAAA

UUUGGCCGUUUU

•is instructions contained in a gene that tell a cell how to make a specific protein

–The amino acid translation of the nucleotide triplets

•Nearly all organisms use an identical genetic code to convert the m R N A codons transcribed from a gene to the amino acid sequence of a polypeptide.

•joins them along one strand of the D N A, following the base-pairing rules.

–A specific nucleotide sequence called a promoter acts as a binding site for R N A polymerase and determines where transcription starts.

In the nucleus, the D N A helix unzips, and R N A nucleotides line up

conveys genetic messages from D N A to the translation machinery of the cell (ribosomes).

Before leaving the nucleus as m R N A, eukaryotic transcripts undergo two modifications:

the product of transcription, carries genetic information from DNA to a ribosome

introns (noncoding segments of R N A) are spliced out “intragenic region”,

exons (the parts of a gene that are expressed) are spliced together

Multiple polypeptides from a single gene

are added to the ends of the m R N A

§Facilitate export out of the nucleus, protect the mRNA from degradation, and help the ribosome bind to the mRNA.

A ribosome attaches to the m R N A and translates its message into a specific polypeptide,

tRNAs transfer amino acids from the ‘cytoplasmic pool’ and add them to the growing polypeptide

–Each t R N A is a folded molecule bearing a base triplet called an anticodon on one end and a specific amino acid attachment site at the other end.

needed for translation. Carries a specific amino acid (coded by mRNA) to the ribosome

are structures in the cytoplasm that coordinate functioning of m R N A and t R N A and catalyze the synthesis of polypeptides

Ribosomes are made of rRNA and proteins and have binding sites for tRNA and mRNA

RNA that (combined with proteins) makes up ribosomes, which translate mRNA into proteins

–mRNA,

–a tRNA bearing the first amino acid, and

–the two subunits of a ribosome.

•DNA transcribed to RNA in the nucleus

•RNA is processed (mRNA) and exits the nucleus (in eukaryotes)

•mRNA and tRNA with a specific amino acid are used by the ribosome to create a polypeptide

•Polypeptide folds into 3-dimensional tertiary structure which determine its function

•are changes in the genetic information of a cell or virus, caused by errors in D N A replication or recombination, or by physical or chemical agents called mutagens.

–Examples of mutagens: high energy radiation such as X-rays or UV light, tobacco products, radioactive substances

•Substituting, inserting, or deleting nucleotides alters a gene, with varying effects.

Elongation continues until a stop codon reaches the ribosome’s A site