foundations of bio exam 3 uiowa

what is a chromosome

single long double helix of DNA wrapped around proteins called histones

what is a gene

segment of DNA that codes for a protein

what are the phases of mitosis

prophase, metaphase, anaphase, telophase

what are the phases of interphase

G1, S, G2

what happens in G1 phase

growth and normal metabolic roles

what happens in S phase

DNA replication

what happens in G2 phase

preparation for mitosis

what is G0

A process where cells are unlikely to divide, but still carry out their normal functions

is DNA polar

yes

DNA synthesizes in the ___ to ___ direction

5' to 3'

what is DNA helicase

enzyme that unzips DNA

what are ssBinding proteins

stabilizes single strands of DNA to prevent unwanted hydrogen bonds between basepairs

what is topoisomerase

corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands

what is primase

lays down an RNA primer

what is DNA polymerase

adds DNA bases complementary to template strand

DNA polymerase cannot replicate DNA unless and RNA primer is first attached to the template strand. This is because DNA polymerase can only ______

add to existing hydroxyl groups

leading: ____ primer(s), lagging: _____ primer(s)

one, multiple

what are okazaki fragments

short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication

what is DNA ligase

creates covalent bonds in the backbone between okazaki fragments

what fills in nucleotides that were once RNA

DNA polymerase

DNA content is doubled after ___ phase

S

one single molecule of DNA is called ___

chromosome

after S phase, when the DNA of a cell has been duplicated, they are arranged in identical pairs call ______ attached by a _____

chromatids, centromere

what is the G1 checkpoint

checks if cell size is adequate, nutrients are sufficient, social signals are present, DNA is undamaged

what is the G2 checkpoint

chromosomes have been replicated successfully, DNA is undamaged, activated MPF is present

what is the M checkpoint

chromosomes have attached to the spindle apparatus, chromosomes have properly segregated and MPF is absent

what are needed to pass G1 checkpoint

cyclin and E2F proteins

how do growth factors promote division

growth factors stimulate cells that produce cyclin and E2F, cyclin binds to Cdk and phosphorylates, Rb inactivates E2F, Cdk phosphorylates Rb, Rb releases E2F, E2F triggers production of S phase proteins

what stops the cell cycle if DNA damage is present

P53

what are autosomes

any chromosome except sex

what is a karyotype

the number and visual appearance of the chromosomes

how many chromosomes do humans have

23 pairs, 46 total

what are homologs

pairs of sister chromatids that have the same genes, but may have different alleles

what is diploid

two sets of chromosomes

what is haploid

one set of chromosomes

2n cells have ___ and ___ chromosomes

maternal and paternal (two sets)

what is the human ploidy

2n = 46

two sets of 23 chromosomes

are two sister chromatids considered a single replicated chromosome

yes, because it is attached it counts as one

what is meiosis I

separation of homologous chromosomes

what is meiosis II

separation of sister chromatids

is meiosis II the same as mitosis

yes

what is a synapsis

pairing of homologous chromosomes

what is a bivalent

a pair of homologous chromosomes

what is crossing over

the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.

what are the stages of meiosis I

Early prophase I

Late prophase I

Metaphase I

Anaphase I

Telophase I

what is early prophase I

chromosomes condense and homolog pairs come together to form a synapsis, bivalent formed

what happens in late prophase I

the two homologs become attached to microtubules from opposite poles of the spindle apparatus; the homologs begin to separate; chromosomes remain joined at chiasmata

what is chiasmata

site of crossing over

what happens during metaphase I

homologous pairs line up in the middle of the cell

what happens in anaphase I

homologous pairs separate

what happens in telophase I

the homologs finish migrating to the poles of the cell - cytokinesis

what are the phases of meiosis II

Prophase II, Metaphase II, Anaphase II, Telophase II

what happens in prophase II

spindles form

what happens during metaphase II

chromosomes line up on metaphase plate

what happens during anaphase II

sister chromatids separate

what happens in telophase II

nuclear envelope forms around each set of chromosomes - cytokinesis

what is the difference between meiosis and mitosis

Meiosis makes 4 different haploid cells Mitosis makes 2 identical diploid cells

what is independent assortment

random distribution of homologous chromosomes

what is down syndrome

trisomy 21 - extra copy of chromosome 21

what is nondisjunction

An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell

what is aneuploidy

the presence of an abnormal number of chromosomes in a cell

what is nondisjunction in meiosis I

Failure of the homologous pairs of chromosomes to seperate

what is nondisjunction in meiosis II

sister chromatids fail to separate

what is trisomy 18

edward's syndrome

when a cell is monosomic, it is lethal in all situations except ____

having a single x chromosome (turner syndrome)

why were garden peas chosen by mendel

inexpensive, easy to grow, short generation time, can control parents, several polymorphic traits

what is a genotype

AaBb

what is a phenotype

physical characteristics of an organism

what is true breeding lines

produced offspring identical to themselves when self fertilized

what are hybrids

mated two different pure lines that differ in traits

what is a monohybrid cross

A cross between individuals heterozygous for a single character

what is a reciprocal cross

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

what is particular inheritance

hereditary determinants do not blend or change

what is the principle of segregation

offspring inherit only one of each allele for a specific gene from each parent

pure line individuals produce offspring with what phenotype

the same (since they are homozygous)

mating between two heterozygous parents produces what ratio of offspring

3:1

what is MPF

mitosis promoting factor; phosphorylates proteins that trigger onset of M phase

short segments of newly synthesized DNA are joined into a continuous strand by ____

ligase

the action of helicase creates ____

replication forks and replication bubbles

progression through the cell cycle is regulated by oscillations in the concentration of which type of molecule

cyclins

what phase of mitosis do chromosomes become visible

prophase

why is decline of cyclin concentration in M phase important

if it did not decline, MPF would be stuck in M phase

what are telomeres

DNA at the tips of chromosomes

how is the aging process linked to telomeres

cells with short telomeres can no longer divide, so damaged tissues cannot be repaired.

what is the ploidy of organisms with two sets of chromosomes

2n

true or false, a haploid organism has one pair of homologous chromosomes

false - they have no pairs, only one set

if a cell has 24 chromosomes, how many chromosomes would each of its four daughter cells have

12

what structure is directly correlated to genetic variability

chiasma

what is the composition of a tetrad at the beginning of prophase I

one pair of homologus chromosomes

if a cell has a diploid number of 50, how many chromosomes are present at the beginning and end of meiosis

50, 25

In human gamete production there is an average of _____ crossover events per chromosome pair

2-3

if 2n = 6 for a given organism, and there is no crossing over, what is the chance the gamete produced will only receive paternal chromosomes

1/8

what is a test cross

crossing an organism with a dominant phenotype but an unknown genotype with one that has a recessive phenotype

if a cell has 38 chromosomes and enters meiosis, how many chromosomes and dna molecules will the daughter cell have

19 chromosomes and 19 double helical DNA molecules

if 2n = 4 for a given organism, and there is no crossing over, what is the chance that a gamete produced by this diploid organism will only receive sperm derived chromosomes

1/4

how would genetic variation be affected if maternal chromosomes always lined up on one side of the metaphase plate during meiosis I and paternal always lined up on the other side

each gamete would inherit either all maternal or all paternal chromosomes

if 2n = 6 and there is no crossing over, what is the chance that a gamete produced will only receive paternal chromosomes

1/8

what three factors lead to most genetic variation in sexually reproducing organisms

independent assortment, random fertilization, crossing over

if a cell has 46 chromosomes and nondisjunction happens in meiosis I, what is the chromosome number in each of the resulting sperm

24, 24, 22, 22

if a cell as 46 chromosomes and non-disjunction happens in meiosis II, what is the chromosome number in each of the resulting sperm

23, 23, 22, 24