DC Human Bio Exam #3

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127 Terms
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The molecule inside cells that contains the genetic information responsible for the development and function of an organism.
a type of protein found in chromosomes.
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the region where a cells spindle fibers attach.
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an individuals complete set of chromosomes.
Homologous Chromosomes
Two chromosome in a pair- normally one inherited from the mother and one from the father.
One of the numbered chromosomes that is not a sex chromosome, 22 pairs.
Sex Chromosome
A type of chromosome involved in sex determination. Females= XX Males=XY
Sister Chromatids
Either of the two identical chromatids that are formed by replication of a chromosome.
How your behaviors and environment can cause changes that affect the way your genes work.
A cell spends most of its time here and it grows, replicates its chromosomes, and prepares for cell division.
Interphase (G1)
The cell makes a variety of proteins that are needed for DNA replication.
Interphase (S)
All of the chromosomes are replicated.
Interphase (G2)
The cell replenishes its energy stores and synthesizes proteins.
A process where a single cell divides into two identical daughter cells.
The first stage of cell division, the chromatids condense and thicken to form distinct bodies.
The second stage of cell division, the nucleus dissolves and the cell’s chromosomes condense and move together, aligning in the center of the cell.
The third stage of cell division, the sister chromatids separate from each other and are pulled towards opposite ends of the cell.
The final stage of cell division, a nuclear membrane forms around each set of chromosomes to separate the nuclear DNA from the cytoplasm.
The process when one cell physically divides into two cells.
Diploid Cell
Having two sets of chromosomes, sexually reproducing organisms
Haploid Cells
The presence of a single set of chromosomes in an organism’s cells. ex. egg and sperm cells.
Examples of somatic cells
muscle cells, blood cells, skin cells, and nerve cells.
Sex cells
gametes, egg cells and sperm.
Role of spindle fibers
to separate the chromosomes, attach to chromosomes during metaphase and pull the chromatids toward opposite poles during anaphase.
egg or sperm cell
the union of two gametes, sperm and egg fuse to form a diploid zygote to initiate development.
Fertilized egg cell that results from the union of a female gamete with a male gamete.
an organism in the early stages of developement.
an unborn baby that develops and grows inside the uterus.
a person between birth and puberty, or between the developmental period of infancy and puberty.
The period in the human lifespan in which full physical and intellectual maturity have been attained.
Crossing over
The exchange of genetic material between non-sister chromatids that occurs during the development of egg and sperm cells.
Independent Assortment
Genes do not influence each other with regard to the sorting of alleles into gametes.
Meiosis 1
The number of cells is doubled but the number of chromosomes is not.
Meiosis 2
The sister chromatids within the two daughter cells separate, forming four new haploid gametes.
Prophase Mitosis
The process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells, chromatin condenses.
Causes abnormal number of chromosomes, ex. down syndrome, trisomy of autosomes
What happens in nondisjunction?
The separation fails to occur causing both sister chromatids or homologous chromosomes to be pulled to one pole of the cell.
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The affected person has three copies of one of the chromosomes instead of two. ex. down syndrome, edward syndrome.
A person is missing one chromosome in the pair. ex. baby born with only one X chromosome (monosomy X)
The basic unit of heredity passed from parent to child, made up of sequences of DNA.
A specific characteristic of an individual.
The alternative form or versions of a gene.
When the allele of a gene effectively overrules the other (recessive) allele.
A trait that is expressed only when genotype is homozygous.
The genetic makeup of an organism.
The observable characteristics in an individual resulting from the expression of genes.

The presence of two identical alleles at a particular gene locus. homo=same

The presence of two different alleles at a particular gene locus.
Law of Segregation
During the formation of gamete, each gene separates from each other so that each gamete carries only one allele for each gene.
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Homozygous dominant
An organism with two dominant alleles for a trait.
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Homozygous recessive
The genotype of an organism with two recessive alleles.
The presence of two different alleles at a particular gene locus.
A person who has one copy of a mutated diesease-causing gene but has no symptoms or mild symptoms.
Complete Dominance
The effect of one allele in a heterozygous genotype completely masks the effect of the other.
Sex-linked Inheritance
Characteristics that are influenced by genes carried on the sex chromosomes. ex. congenital night blindness, high blood pressure genes.
Incomplete Dominance
A form of gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype.
Multiple Alleles
The alternative forms of the same gene so they influence the same trait. ex) ABO blood type.
Two alleles are expressed to an equal degree within an organism.
Female Pedigree Shape
Male Pedigree Shape
Affected Pedigree
Fully shaded
Unaffected Pedigree
Not shaded
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The expression of multiple traits by a single gene.
Polygenic Inheritance
When one characteristic is controlled by two or more genes. ex) height, skin color, eye color, etc.
Linked genes
When genes are located on the same chromosome and cannot segregate independently b/c they are inherited together.
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Organic molecule with a basic composition of a nitrogenous base, pentose sugar, and phosphate.
4 types of nucleotides
Adenine, Cytosine, Guanine, and Thymine.
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DNA Structure
Double Helix, two complementary strands of nucleotide held together by hydrogen bonds.
Hydrogen Bonds
Interaction involving a hydrogen atom located between a pair of other atoms having a high affinity for electrons.
Covalent Bonds
The sharing of electron pairs between atoms.
Base-pairing rules
In DNA, Adenine with Thymine, Cytosine with Guanine. In RNA, Adenine pairs with Uracil.
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Breaks the hydrogen bonds and opens up the DNA strand.
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DNA Polymerase
Links DNA nucleotides together to form the daughter strand during replication.
RNA Polymerase
Builds mRNA
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Catalyzing the reaction of joining two large molecules by establishing a new chemical bond.
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Semiconservative model of replication
After one round of replication, every new DNA double helix would be a hybrid that consisted of one strand of old DNA bound to one strand of newly synthesized DNA.
The process of making an RNA copy of a gene’s DNA sequence.
A cell makes proteins using the genetic information carried in messenger RNA.
Role of mRNA
To carry protein information from the DNA in a cell’s nucleus to the cells cytoplasm.
Role of tRNA
Adaptor between the genetic instructions written in nucleic acid sequences and the protein products encoded in genes.
Role of rRNA
Direct the catalytic steps of protein synthesis.
A three-nucleotide sequence found on tRNA that binds to the corresponding mRNA sequence.
A three-nucleotide or triplet sequence found on mRNA that codes for a certain amino acid during translation.
Amino acid
Molecules that combine to form proteins.
Peptide bond
Covalent bond formed between two amino acids.
RNA Polymerase
Synthesizes RNA molecules from a template of DNA through a process called transcription.
\-RNA contains the sugar ribose, while DNA contains the slightly different sugar deoxyribose. \-RNA is single stranded, DNA is double stranded. \-RNA has a short chain of nucleotides, DNA has a long chain of nucleotides.
Noncoding sections of RNA transcript that are spliced out before the RNA molecule is translated into a protein.
The sections of DNA or RNA that code for proteins.
Responsible for synthesizing proteins by translating the genetic code transcribed in mRNA into an amino acid sequence.
Role of start/stop codon
The start codon marks the site at which translation into protein sequence begins, and the stop codon marks the site at which translation ends.
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A mutation that exchanges one base for another.
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The loss of one or more nucleotides from a segment of DNA.
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Involves the addition of one or more nucleotides into a segment of DNA.
Frame-shift Mutation
An insertion or deletion involving a number of base pairs that is not a multiple of three, which consequently disrupts the triplet reading frame.
DNA Profiling

The process where a specific DNA pattern is obtained from a person or a sample of bodily tissue, often used in investigations.

Restriction Enzymes

A protein isolated from bacteria that cleaves DNA sequences at specific sites, producing DNA fragments with a known sequence at each end.


Laboratory technique for rapidly producing millions to billions of copies of a specific segment of DNA.


A technique scientists use to make exact copies of living things.

Recombinant DNA

Using enzymes and various laboratory techniques to manipulate and isolate DNA segments of interest.

Gene Therapy

The use of genetic material to treat or prevent disease.

Key Steps to the origin of life

-Simple inorganic chemicals form more complex, organic ones.

-Macromolecules form.

-Self-replicating molecules form genetic material

-Large, organic molecules get encased within lipid droplets.

-Prokaryotic cells form

-Endosymbiosis leads to eukaryotic cells

-Multicellular organisms arise.


The development of entire groups. ex) tetrapods which are animals with four limbs.


Formation of new and distinct species in the course of evolution.


Change within a species or small group of organisms ex) mosquitoes evolving resistance to DDT.

Genetic Drift

The change in frequency of an existing gene variant in the population due to random chance.

Founder Effect
Reduced genetic diversity which results when a population is descended from a small number of colonizing ancestors.
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Bottleneck effect
Example of genetic drift that happens when the size of a population is severely reduced, b/c of events like natural disasters.
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Gene Flow

Any movement of individuals, and/or the genetic material they carry, from one population to another.

Natural Selection

The process by which organisms better adapted to their environment tend to survive and reproduce more than those less adapted to their environment.

Allele Frequency

How common an allele is in a population.

Fossil Evidence

Provides a record of how creature evolved.

Homologous Structures

Same structures/bones but somewhat different from common ancestor.

Analogous Structure

Similar structures but not from common ancestors.

Vestigial Structures

Structures that have no current purpose, ancestors used them ex) wisdom teeth

Comparative Embryology

The comparison of embryo development across species.

Hominid Characteristics

Bipedalism, big brain, tool use

Domain of humans


Kingdom of Human


Phylum of humans


Class of humans


Order of humans


Family of humans


Genus of humans


Species of humans


Out of Africa Hypothesis

Humans evolved in East Africa, dispersing to populate the rest of the world from 70,000 years ago, replacing, the archaic hominins that were resident outside of Africa.