BI 221 Final

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cell cycle

series of events that cells go through as they grow and divide

G1 checkpoint

Checks the surroundings to make sure the conditions are favorable and the cell is healthy enough to enter the next stage

G2 checkpoint

The cell checks to make sure the DNA is copied correctly

M checkpoint

Spindle assembly checkpoint. Mitosis will not continue if chromosomes are not properly aligned.

benign tumor

A mass of abnormal cells with specific genetic and cellular changes such that the cells are not capable of surviving at a new site and generally remain at the site of the tumor's origin.

malignant tumor

An abnormal tissue mass that can spread into neighboring tissue and to other parts of the body; a cancerous tumor.

metastasis

spread of cancer cells beyond their original site in the body

Proto-oncogenes

normal cellular genes that are important regulators of normal cellular processes, they promote growth.

Oncogenes

mutated forms of proto-oncogenes that cause normal cells to grow out of control and become cancer cells

tumor suppressor genes

A gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growth that contributes to cancer.

Purine

a nitrogenous base that has a double-ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; either adenine or guanine

Pyrimidines

a nitrogenous base that only has a single ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; either thymine, cytosine, or uracil

Polymer

A long molecule consisting of many similar or identical monomers linked together.

DNA backbone

5' to 3' phosphodiester bonds form phosphate backbone

phosphodiester bond

the type of bond that links the nucleotides in DNA or RNA. joins the phosphate group of one nucleotide to the hydroxyl group on the sugar of another nucleotide

semi-conservative replication

in each new DNA double helix, one strand is from the original molecule, and one strand is new

conservative replication

Conservative replication is a theoretical method of replication where the original strands of DNA are left intact and two new strands are formed bonded together.

dispersive replication

a disproved model of DNA synthesis suggesting more or less random interspersion of parental and new segments in daughter DNA molecules

Primase

An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.

single strand binding proteins

bind to the unpaired DNA strands, keeping them from re-pairing

Topoisomerase

Enzyme that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.

DNA polymerase III

synthesizes new DNA only in the 5' to 3' direction

DNA polymerase I

removes the RNA primer and replaces it with DNA

DNA ligase

an enzyme that eventually joins the sugar-phosphate backbones of the Okazaki fragments

Helicase

An enzyme that untwists the double helix of DNA at the replication forks.

Okazaki fragments

Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

nucleotide triphosphate

origin of replication

Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.

replication fork

A Y-shaped region on a replicating DNA molecule where new strands are growing.

Centromere

Area where the chromatids of a chromosome are attached

Euchromatin

The less condensed form of eukaryotic chromatin that is available for transcription.

Heterochromatin

Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.

Histones

protein molecules around which DNA is tightly coiled in chromatin

Gamates

reproductive cells

chromosome number

The total number of chromosomes in a cell of a given species.

Karyotype

A display of the homologous chromosome pairs of a cell arranged by size and shape.

somatic cells

body cells

Ploidy

number of sets of chromosomes in a cell

homologous chromosomes

Chromosomes that have the same sequence of genes, that have the same structure, and that pair during meiosis.

Haploid

having a half set of chromosomes

Diploid

2 sets of chromosomes

asexual reproduction

A reproductive process that involves only one parent and produces offspring that are identical to the parent.

sexual reproduction

Process by which cells from two different parents unite to produce the first cell of a new organism.

Fertilization

Fusion of an egg and sperm cell

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

chiasmata

site of crossing over

synapsis

the fusion of chromosome pairs at the start of meiosis.

Recombination

the genetic process by which one chromosome breaks off and attaches to another chromosome during reproductive cell division

law of independent assortment

Each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results are random

recombinant chromosomes

A chromosome created when crossing over combines the DNA from two parents into a single chromosome.

Allele

An alternative form of a gene.

dihybrid cross

Cross or mating between organisms involving two pairs of contrasting traits

Law of Dominance

In many traits one allele is dominant over the other allele. The "weaker recessive" allele is only expressed when it is paired with another recessive allele

Genotype

genetic makeup of an organism

Phenotype

An organism's physical appearance, or visible traits.

Heterozygous

An organism that has two different alleles for a trait

Homozygous

An organism that has two identical alleles for a trait

Law of Segregation

Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete

locus

Location of a gene on a chromosome

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

P generation

parent generation

F1 generation

the first generation of offspring obtained from an experimental cross of two organisms

F2 generation

the second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation

progeny

offspring

testcross

cross between an organism with an unknown genotype and an organism with a recessive phenotype

true-breeding

term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate

Pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family.

product rule of probability

The chance of two or more independent events occurring together is the product of their chance of occurring separately

sum rule of probability

the chance of an event that can occur in more than one way is the sum of the individual chances

independent events

The outcome of one event does not affect the outcome of the second event

mutually exclusive events

events that cannot happen at the same time

Carrier

A person who has one recessive allele for a trait, but does not have the trait.

plieotropy

The ability of a single gene to have multiple phenotypic effects.

epistatis

gene at one locus on the chromosome alters the phenotypic expression of a gene at different locus

Co-dominance

A pattern of inheritance in which the phenotypic effect of two alleles in a heterozygous genotype express each phenotype of each allele fully and equally; a phenotype which would not be expressed in any other genotypic combination.

incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

polygenic inheritance

occurs when multiple genes determine the phenotype of a trait

heterogametic

sex chromosomes are of different types

homogametic

sex chromosomes are of one type

sex linkage

the presence of a gene on a sex chromosome

Autosomes

Any chromosome that is not a sex chromosome

wildtype

the most common genotype/phenotype observed in a population

X-linked

referring to a gene located on the X chromosome

SRY gene

the sex determining region of the Y chromosome in males. Encodes the testis-determining factor, which turns the primordial gonads into the testes

sex determination

The biological mechanism that determines whether an organism will develop as a male or female

sex-limited traits

a characteristic controlled by autosomal genes that is phenotypically exhibited in only one of the two sexes.

sex-influenced traits

an autosomal trait that is influenced by the presence of male or female sex hormones

sex chromosomes

Chromosomes that determine the sex of an individual

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

nondisjunction in meiosis I

4 abnormal gametes, 2 with chromosome duplicated, 2 with corresponding chromosomes missing

nondisjunction in meiosis II

2 normal gametes, 2 abnormal gametes

Aneuploidy

Abnormal number of chromosomes.

X inactivation

one of two X chromosomes is randomly inactivated and remains coiled as a Barr body

Barr body

A dense body formed from a deactivated X chromosome.

gene linkage

the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction

Trisomy

3 copies of a chromosome

recombinants

offspring whose phenotype differs from that of the parents

recombination frequency

the percentage of recombinant offspring among the total. (number of recombinants/total number of offsprings)x100%

Monosomy

Chromosomal abnormality consisting of the absence of one chromosome from the normal diploid number

alternative splicing

Splicing of introns in a pre-mRNA that occurs in different ways, leading to different mRNAs that code for different proteins. Increases the diversity of proteins.