Genetics test dos

G1 phase

chromosomes are NOT duplicating or dividing

S phase

duplication of chromosomes into sister chromatids

G2 phase

sythesis of proteins required for mitosis

1. Prophase

• chromosomes condense and become visible

• Centrosomes move apart toward opposite poles

• Nucleoli begin to disappear

2. Prometaphase

• nuclear envelope breaks down

• microtubules from centrosomes invade the nucleus and connect to kinetochores in centromere of each chromatid

3. Metaphase

• chromosomes align on the metaphase plate with sister chromatids facing opposite poles

• Forces pushing and pulling chromosomes to or from each pole are in balanced equilibrium

4. Anaphase

• centromeres of all chromosomes divide simultaneously

• Kinetochore microtubules shorten and pull separated sister chromatids to opposite poles

Telophase

• nuclear envelope forms around each group of chromatids

• nucleoli re-form

• spindle fibers disperse

• chromosomes decondense

Cytokinesis

parent cells split into two daughter cells with identical nuclei

Leptotene

• chromosomes thicken and become visible, but chromatids remain invisible

• Centrosomes begin to move toward opposite poles

Zygotene

• homologous chromosomes enter synapsis

• the synaptonemal complex forms

Pachytene

• synapsis is complete

• crossing over

Diplotene

• Synaptonemal complex dissolves

• a tetrad of four chromatids is visible

• Crossing over points appear as chiasmata

• Meiotic arrest occurs at this time in many species

Diakinesis

• chromatids thicken and shorten

• At the end of prophase I, the nuclear membrane breaks down and spindle begins to form

Metaphase I

• Tetrads line up along the metaphase plate

• Each chromosome of a homologous pair attaches to fibers from opposite poles

• Sister chromatids attach to fibers from the same pole

Anaphase I

• Sister centromeres remain connected to each other

• The chiasmata dissolve

• Homologous chromosomes move to opposite poles

Telophase I

• The nuclear envelope re-forms

• Resultant cells have half the number of chromosomes, each consisting of two sister chromatids

• Cytokinesis separates the daughter cells

Interkinesis

• This is similar to interphase with one important exception: No chromosomal duplication take place

• In some species the chromosomes decondense

• between Meiosis I and II

Prophase II

• chromosomes condense

• Centrioles move toward the poles

• the nuclear envelope breaks down at the end of prophase II

Metaphase II

• chromosomes align at the metaphase plate

• sister chromatids attach to spindle fibers from opposite poles

Anaphase II

• sister centromeres detach from each other, allowing sister chromatids to move to opposite poles

Telophase II

Chromosomes begin to uncoil

Nuclear envelopes and nucleoli re-form

Cytokinesis

• the cytoplasm divides, forming four haploid cells

a. anaphase of mitosis

96, 96

b. anaphase I of meiosis

48, 96

c. anaphase II of meiosis

48, 48

d. G1 prior to mitosis

48, 48

e. G2 prior to mitosis

48, 96

f. G1 prior to meiosis I

48, 48

g. Prophase of meiosis I

48, 96

i. an oogonial cell prior to S phase

48, 48

ii. a spermatid

24, 24

iii. a primary oocyte arrested prior to ovulation

48, 96

iv. a secondary oocyte arrested prior to fertilization

24, 48

v. a secondary polar body

24, 24

vi. chimpanzee sperm

24, 24

YyRr x YyRr

9:3:3:1

recessive epistasis

homozygous recessive alleles at one specific gene locus mask the expression of alleles at another locus

reciprocal recessive epistasis

homozygous alleles at either of two loci can mask the other

Metacentric chromosome

centromere is in the middle

Acrocentric chromosome

centromere is near one end

Homologs

contain the same set of genes, but can have different alleles for some genes (one from mom and one from dad)

Interphase

has 3 parts: gap 1 (G1) phase, synthesis (S) phase, and gap 2 (G2) phase

Mitosis

divides chromosomes equally to two genetically identical daughter cells

Centrosome

microtubule organizing center near the nuclear envelope

Centrioles

core of centrosome not found in plant cells

contractile ring

contract to from cleavage furrow in animal cells during cytokinesis

cell plate

forms near equator of plant cells during cytokinesis

at checkpoints (3)

prior events must be completed before the next step of the cycle can begin

somatic cells

make up the vast majority of cells in the organism (enter mitosis)

Germ cells

precursors to gametes (enter meiosis)

nondisjunction

homologs of a chromosome pair do not segregate during meiosis I

Independent assortment of homologs

creates different combinations of alleles

Crossing over between homologs

creates different combinations of alleles within each chromosome

germ line

specialized diploid cells set aside during embryogenesis

gametogenesis

the formation of gametes

oogonia

diploid germ cells in ovaries of female embryos

spermatogonia

diploid germ cells found only in testis, divide by mitosis to form primary spermatocytes

SRY

single gene that is the primary determinant of maleness

pseudoautosomal regions (PARs)

enable sex chromosomes to pair during meiosis I

Barr body

inactive x chromosome that condenses in female cells

biopotential cells (SRY dependent)

• gonad precursors

• external sex organ precursors

female/male sex organ precursors

are specific to each sex

testes secrete 2 hormones:

testosterone and AMF

testosterone

stimulates precursor cells to form male sex organs

AMF

inhibits female internal sex organ formation

inheritance of mutant AMFR

results in complete male sex organs plus internal female sex organs

complete androgen insensitivity syndrome

mutant androgen receptor and mutant AMF receptor results in no male/female internal sex organs

heterogametic sex

two different kinds of gametes (XY)

Homogametic sex

one type of gamete (XX)

Hemizygous

having only one copy of a gene in an otherwise diploid organism (X-linked genes in males)

x linked recessive

• mutation never passes from father to son

• daughters of affected males are carriers- ½ of sons of carriers will inherit the trait

x linked dominant

• trait seen in every generation

• affected male will produce affected daughters and unaffected sons

Y linked

only in males

sex influenced traits

appear in both sexes but hormonal differences may cause difference (male pattern baldness)

sex limited traits

affect a structure or process found in only one sex

syntenic genes

genes located on the same chromosome

linked genes

genes close enough together that they are inherited together

Chi square test

2-point test cross

1 parent should be heterozygous for both genes and the other should be homozygous recessive

Recombination frequency

bacteriophages

viruses that infect bacteria

phosphodiester bonds

covalent bonds joining adjacent nucleotides, always form covalent link between 3’ carbon of one nucleotide and 5’ carbon of the next nucleotide

5’ end of chain

phosphate group

3’ end of chain

hydroxyl group from deoxyribose sugar

Chargaff’s rule

A pairs with T and C pairs with G

Base pairs consist of

hydrogen bonds between a purine (A,G) and pyrimidine (C,U,T)

G-C pairing

3 hydrogen bonds

A-T pairing

2 hydrogen bonds

DNA sequences are read

5’ —> 3’

3 point crosses result in

8 potential F2 classes

Exons

coding sequences

Semiconservative

the Watson Crick model

Conservative

parental double helix remains intact, both strands of daughter helices are newly synthesized

Dispersive

both strands of both daughter helices contain original and newly synthesized DNA

1. Initiator protein

binds to the origin of replication

2. Helicase

unwinds the helix

3. Single-strand binding proteins

keep the DNA helix open

4. Primase

synthesizes RNA primers

5. RNA primers

are complementary and antiparallel to each template strand