Genetics exam 1

effects of mutations on evolution

Increases genetic variation.

Codon

Any sequence of three adjacent nucleotides in a messenger

RNA molecule, specifying either an amino acid or a stop

signal in protein synthesis.

Gene

Parts of DNA that code for making proteins

Genome

An organism’s complete set of DNA

Polymorphisms

The presence in a population of two or more relatively

common forms of a gene, chromosome, or genetically

determined trait.

Proteome

The complete set of proteins encoded in the genome.

Transcript

An RNA strand that is produced from, and is

complementary in base sequence to, a DNA template

strand.

Nitrogenous bases of DNA

adenine, thymine, cytosine, and guanine

Central dogma

DNA codes for RNA, and RNA codes for protein. The DNA → RNA step is transcription, and the RNA → protein step is translation.

Locus

The site or position of a particular gene on a chromosome.

Allele

Any of the alternative forms of a given gene.

testcross

Cross an unknown dominant with a known recessive trait.

true-breeding

When offspring produced are same as the parent.

Differentiate between homozygote recessive, homozygote dominant, heterozygote

An organism can be homozygous dominant, if it carries two copies of the same dominant allele, or homozygous recessive, if it carries two copies of the same recessive allele.Heterozygous means that an organism has two different alleles of a gene.

Chargaff’s Rule

In double-stranded DNA, the amount of A equals that of T,

and the amount of G equals that of C.

codominance

type of inheritance in which two alleles of the same gene are expressed separately to yield different traits in an individual

Variable expressivity

Range of phenotypic expression

Incomplete penetrance

Condition in which a mutant phenotype is not expressed in

all organisms with the mutant genotype.

sex-linked trait

Related to a trait determined by a gene on a sex

chromosome, usually the X.

Mendel's Principle of Segregation

each individual that is a diploid has a pair of alleles (copy) for a particular trait.

Centromere

Region of chromosome that contains spindle fibers. It is a specialized DNA sequence between sister chromatids, where mitotic spindle attaches.

chiasma

site of crossing over

Independent Assortment

the alleles of two or more different genes get sorted into gametes independently of one another.

How is DNA packaged?

Tightly wrapped with histones without breaking

What is cell division?

The parent cell divides into two "daughter" cells. The process then repeats.

What is the purpose of cell division

the production of gametes and growth in eukaryotes.

genetics

study of biologically inherited traits

genomics

study of all genes in an organism

trait

a characteristic coded for by genes

mutation

any heritable change in a gene

mutant

the result of a mutation

polymorphic

a gene that has two or more variants, or alleles

pleiotropy

The ability of a single gene to have multiple effects

preotome

totality of proteins coded for in a genome

nucleoside

a nitrogen base joined with a deoxyribose molecule

nucleotide

a nucleoside combined with a phosphate group

transposable element

a DNA sequence capable of moving from one site to another within a genome

particulate gene

the concept that a gene is unchanged as it is passed from one generation to another

pedigree

family tree diagram that shows the phenotype of each individual

penetrance

the proportion of people with the at-risk genotype that express traits of the disorder

incomplete dominance

a type of inheritance when the heterozygote shows an intermediate form of both the dominant and recessive phenotypes

codominance

a type of inheritance when neither trait dominates over the other, and the heterozygote shows both the dominant and recessive phenotypes

epistasis

one gene will mask expression of the other

chromatin

the unwound form of DNA; "beads on a string"

centrosome

organelles which serve as the main microtubule organizing centers

centromere

specialized DNA sequence between sister chromatids, where mitotic spindle attaches

nucleosome

structural unit of DNA packaging, consisting of DNA wrapped around histone proteins

apoptosis

programmed cell death as a part of controlled cell division

proto-oncogenes

genes that stimulate cell division or apoptosis at division checkpoints

oncogenes

mutated porto-oncogenes, cause unregulated cell division

cytogenetics

the field of genetics that involves the microscopic examination of chromosomes

cancer

unregulated cell division

karyotype

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

histone

group of basic proteins found in chromatin

tumor-suppressor genes

genes that promote apoptosis in cell division

gain of function mutation

a mutation that allows for enhances expression of a gene

loss of function mutation

a mutation that inhibits the expression of a gene

contact inhibition

a process that stops additional cell growth when cells become crowded

tumor

mass of cells or tissue with no function

benign

tumor that stays in one place

malignant

tumor that invades other tissues

angiogenesis

the development of new blood vessels

anchorage dependence

the requirement that to divide, a cell must be attached to a solid surface.

telomere

protective cap at the end of the chromosome that regulates cell death

pyrimidine bases

thymine and cytosine

purine bases

adenine and guanine

chromomeres

localized contractions with a characteristic number, size, and position in a given chromosome

longest stage in meiosis

Prophase I

leptotene period of meiosis I prophase I

when the DNA is visible only as a thin thread in the nucleus

zygotene period of meiosis I prophase I

when homologous chromosomes synapse together at the ends

pachytene period of meiosis I prophase I

when chromosomes shorten & thicken and crossing over occurs

diplotene period of meiosis I prophase I

when synapsed chromosomes pull apart but are held together by the chiasma

diakinesis of meiosis I prophase I

when the nuclear envelope breaks down, spindle fibers form, and the DNA is fully condensed

Meiosis I Prophase I

homologous chromosomes pair up and crossing over occurs.

Meiosis I Metaphase I

homologue pairs line up at the metaphase plate for separation.

Meiosis I Anaphase I

the homologues are pulled apart and move apart to opposite ends of the cell.

Meiosis I Telophase I/Cytokinesis

the chromosomes arrive at opposite poles of the cell and nuclear membrane reassembles.

chiasma

site of crossing over

Chromatid

one half of a duplicated chromosome

Identify the cell cycle checkpoints

G1, G2, M

G1 phase

the cell grows physically larger, copies organelles, and makes the molecular building blocks it will need in later steps.

S phase

the cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates the centrosome.

G2 phase

the cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis.

The daughter cells from mitosis are called

diploid cells

What are the steps in cell division for mitosis?

prophase, prometaphase, metaphase, anaphase, and telophase

Prophase

Chromosomes condense and are visible under a microscope. Each chromosome made of 2 sister chromatids. Spindle fibers form that radiate from the centrioles on either side of the cell

Prometaphase

The mitotic spindle begins to capture and organize the chromosomes. The chromosomes become even more condensed, so they are very compact. The nuclear envelope breaks down, releasing the chromosomes.

Metaphase

Chromosomes meet on the metaphase plate. They are most highly condensed during this stage

Anaphase

Centromere of each chromosome splits that allow sister chromatids to separate. Microtubules not attached to chromosomes elongate and push apart, separating the poles and making the cell longer.

What is the difference between mitosis and meiosis?

1. Mitosis: Two diploid (2n) somatic cells that are genetically identical to each other and the original parent cell.


2. Meiosis:four haploid (n) gametes that are genetically unique from each other and the original parent (germ) cell.
3. Mitosis involves one cell division, whereas meiosis involves two cell divisions.

Describe how meiosis creates genetic variation

Random alignment increases the number of possible chromosome combinations in the gametes.

Meiosis II phases

Prophase II: Starting cells are haploid cells made in Meiosis I. Chromosomes condense, nuclear envelope breaks.

Metaphase II: Chromosomes line up at metaphase plate

Anaphase II: The sister chromatids separate and are pulled towards opposite poles of the cell.

Telophase II: Nuclear membranes form around each set of chromosomes, and the chromosomes decondense. Newly forming gametes are haploid. Each chromosome has one chromatid.

Cancer v normal

Cancer keep duplicating and normal cells stop.

Normal cells have contact inhibition.

Wild type

natural un mutated form

role of mutations in evolution

Creating genetic variation.

Causes non disjunction

Metaphase

Nondisjunction

Unequal distribution of chromosome

Chromosome

One or more unique pieces of DNA

Telophase

Ends with 2 daughter cells. Each have a full set of chromosomes. The mitotic spindle is broken down into its building blocks. The chromosomes begin to decondense and return to their “stringy” form.