PCB3063 Exam 1 Dr. Cui

Genetics

Scientific study of heredity and variation

Traits are controlled by

genes

Gene

A segment of DNA that codes for a specific trait

DNA

deoxyribonucleic acid, carrier of genetic information

central dogma or molecular biology

DNA -> RNA -> Protein; some genes do not encode proteins such as rRNAs and tRNAs

Genes are carried on

chromosomes

Chromatin

an array of acidic and basic proteins into thin fibers

Chromosomes

condensed and coiled form of chromatin

The cytoplasm contains a

genome that results in female dominance

Pure-breeding

Individuals that are homozygous that will always produce the same offspring when crossed together

The chromosomal theory of inheritance states that

inherited traits are controlled by genes residing on chromosomes (Waltor, 1903)

each trait is controlled by

pair of genes

Genes are transmitted through

gametes

What is special about model organisms

easy to grow, have short life cycles, produce many offspring, and offer straightforward genetic analysis

Alternate form of a gene is called

allele

Mutations

a random error in gene replication that leads to a change

Genotype

genetic makeup of an organism

Phenotype

An organism's physical appearance, or visible traits.

Allele

Different forms of a gene

ABO blood groups

based on having an A, B, both or no antigens on red blood cells

A phenotype

AO or AA

B phenotype

BB, BO

O phenotype

OO genotype

AB phenotype

AB genotype

one unreplicated chromosome

one replicated chromosome

2 sister chromatids but one chromosome

In this stage there is one DNA helix

G1 phase

Two DNA double helices are present in the

G2 phase

Interphase

Cell grows, performs its normal functions, and prepares for division; consists of G1, S, and G2 phases

Prometaphase

chromosomes are clearly double structures; centrioles reach the opposite poles; spindle fibers form

sister chromatids are held together by

cohesin

cohesion

multi subunit protein complex

cohesion is degraded by

separase

cohesion is protected by

shugoshin

Centrioles

Cell organelle that aids in cell division in animal cells only

centrioles function

organize DNA during cell division

Most organisms are

diploid

Diploid

2 sets of chromosomes (2n)

homologous chromosomes

chromosomes that carry the same sets of genes but might have different alleles

Centromere

Area where the chromatids of a chromosome are attached

sex chromosomes

homologous but do not carry the same genes

Haploid

an organism or cell having only one complete set of chromosomes

Polyploidy

condition in which an organism has extra sets of chromosomes

Mitosis

Mitosis produces

2 identical daughter cells

Karyotype

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

chromosomes are recognized by

their centromere position

metacentric

centromere in middle

acrocentric

centromere close to end

telocentric

the centromere is at or very near the end of the chromosome

Mitosis is responsible for

growth, wound repair, asexual reproduction

Karyokinesis

division of the nucleus

Cytokinesis

division of the cytoplasm

S phase

DNA replication

G0 phase

A nondividing state occupied by cells that have left the cell cycle, sometimes reversibly.

cell cycle control kinases

promote the manufacture and activity of proteins required for DNA synthesis

Cyclins

proteins that regulate the timing of the cell cycle in eukaryotic cells

If the checkpoints fail to recognize and stop the errors, then cell division proceeds and a....... results

tumor

Practice Questions

At which stage of the cell cycle does DNA replication occurs?

A. Interphase

In what status the chromosome exist immediately after replication?

A. Extended and amorphous

Which of the following chromosome pairs are identical in adiploid cell?

A. sister chromatids

Meiosis

Creates 4 haploid gamete cells from a diploid cell and enhances genetic variation

meiosis 1

reproduction process that halves the # of chromosomes and results in diploid cells

Meiosis II

sister chromatids separate

synapsis

Pairing of homologous chromosomes

Recombination

shuffling the parental genetic alleles

Chiasma

site of crossing over

Tetrad

structure containing 4 chromatids that forms during meiosis

prophase 2

The duplicated chromosomes and spindle fibers reappear in each new cell.

metaphase 2

Chromosomes line up at the equator.

anaphase 2

sister chromatids separate and move to opposite poles

telophase 2

A nuclear membrane forms around the chromosomes in each of the 4 new cells.

special events in meiosis 1

- Homologous chromosomes pairs, forming tetrads

- Chromosome recombination (crossing over) occurs, shuffling the parental genetic materials

- Homologous chromosomes are separated into different daughter cells

special events in meosis 2

Sister chromatids are separated into different daughter cells

outcome of meiosis

chromosome number halved, parental genome shuffled, gamete of various genotypes are produced.

crossing over occurs during

meiosis 1 prophase 1 and produces independetly into gametes

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

[..] restores the diploid number

fertilization

allows multi-generation comparisons

seed storage

Mendel

had four postulates, two became laws, discovered the basis of diploid genetics

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

P1 generation

parent generation

F1 generation

offspring of the P generation

F2 generation

offspring of the F1 generation

F2 generation results from

the selfing of f1

reciprical cross

a cross in which the phenotypes of the male and female are reversed compared with a prior cross

Mendel's first three postulates

1. Each trait is controlled by a pair of factors GENES

2. When 2 different factors for a trait are present in an individual one is DOMINANT and one is RECESSIVE

3. During gamete formation the paired factors SEGREGATE RANDOMLY

Homozygous

having two identical alleles for a trait

Heterozygous

having two different alleles for a trait

monohyprid cross ratios

phenotype 3:1

genotype 1:2:1

1st postulate: Unit factors in pairs

genetic characters are controlled by unit factors existing in pairs in individual organisms

2nd postulate: dominance/recessiveness

In the pair of unlike unit factors for a single characteristic in an individual, one unit factor is dominant and the other is recessive.

3rd postulate: Segregation (became Mendel's 1st law)

The paired unit factors segregate (separate) independently during gamete formation.

testcross

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

Spermatogenesis

production of sperm

Oogenesis

Egg production

dihybrid cross

A cross between individuals that have different alleles for the same gene; 2 factor cross

pehnotypic ratio for dihybrid cross

9:3:3:1

Mendel's fourth postulate (second law)

-during gamete formation, segregating pairs of unit factors assort independently of each other.

-all possible combinations of chromatids in the gametes will form with equal frequency