BIO-110 Quiz 7 Flashcards

What are the pairs called that chromosomes come in

homologous pairs (one from each parent)

what does homologous pairing mean and what does this mean fro the chromosome

they carry the same genes as each other, but there are slight variations in each gene

alleles

the matched genes that code for the same protein

sex chromosomes are more different from each other compared to what

homologous pairs of autosomes

meiosis involves

two divisions, yielding 4 daughter cells with the ½ the chromosomes of the parent cell

what does sexual reproduction allow for

genetic variation between each generation

what does genetic variation allow for

• adaptation to changes in environmental conditions

• flexibility

ploidy

the number of sets of chromosomes

humans are mostly….

diploid (2 sets)

though human gametes are…

haploid (1 set)

many plants and non-mammalian vertebrates are….

tetraploid (4 sets)

ploidy can vary over…

• organisms life cycle

• between different cell types within an organism

multiples of the same chromosomes are called

homologous chromosomes

meiosis 1:

parent cells is diploid (2n) and contains a homologous pair of replicated chromosomes

meiosis 2:

daughter cells are haploid (n) and contain just one homolog

four daughter cells contain…

one unreplicated chromosome each

in animals, the four haploid daughter cells in meiosis can develop into what?

gametes

what does meiosis give a diploid organism

haploid gametes

in order to reproduce we must combine what?

two gametes in order to reconstitute a full genome

diploid offspring contains what

homologous pair of chromosomes

meiosis I

1. interphase (uncondensed chromosomes replicate in parent cell)

2. early prophase I

3. late prophase I

4. metaphase I

5. anaphase I

meiosis II

6. telophase I

7. prophase II

8. metaphase II

9. anaphase II

10. telophase II

meiosis I: interphase

• prepare for cell division

• synthesis happens as normal, replicating the genome

what are the two distinctions from prophase in mitosis vs prophase in meiosis

• in meiosis, with early prophase I, it involves pairing of homologous chromosomes (synapsis)

• in meiosis with late prophase I, non-sister chromatids begin to separate but remain joined at some points

chiasma

the points where the chromatid are still joined

what happens at chiasmata

the chromosomes break and exchange pieces which is called crossing over

summary of prophase

1. replication during interphase

2. synapsis, during prophase I

3. crossing over, during prophase I

synapsis

the pairing of homologous chromosomes

what does early prophase I of meiosis form

tetrads or bivalents which are two pairs of sister chromatids

what are the chromatids from different homologous chromosomes called

non-sister chromatids

crossing over usually occurs

at least once in each non-sister chromatid

meiosis I: metaphase I

each tetrad moves to the metaphase plate, half as many tetrads lined up compared to mitosis due to the pairing, which doesn’t happen in mitosis as they line up individually

how many tetrads are lined up during meiosis I metaphase

23 tetrads (each = 2 chromosomes)

what is the orientation like for each tetrad in meiosis I: metaphase I

each tetrad is random

each tetrad in meiosis I: metaphase I has a 50/50 chance of…

having the maternal or paternal chromosome on a particular side

meiosis I: anaphase I

• each tetrad is pulled apart and moved to opposite sides of the cell

• sister chromatids from each maternal or paternal chromosome stay together, but are not identical anymore as they carry new combos of genetic material

meiosis I: telophase I

homologous chromosomes move to opposite sides

meiosis I: cytokinesis I

• finished meiosis I

• yields two haploid cells (CHROMOSOMES ARE STILL REPLICATED)

meiosis II

two daughter cells now proceed thru all of the phases of meiosis (except just no prophase)

in mitosis:

46 replicated chromosomes are split, yielding 2 daughter cells w/ 46 unreplicated chromosomes

in meiosis I:

23 tetrads are split, yielding 2 daughter cells with 23 replicated chromosomes each

meiosis II:

23 replicated chromosomes are split (in each daughter cell), yielding 4 daughter cells w/ 23 unreplicated chromosomes each

nondisjunction

the failure of either homologous chromosomes (meiosis I) ir sister chromatids (meiosis II) to separate

nondisjunction leads to…

some daughter cells w/ too many and some w/ too few chromosomes

daughter cells getting too many chromosomes is called

trisomy

daughter cells getting too few chromosomes is called

monosomy

errors in meiosis happens to how many of all human zygotes?

1/3

aneuploid cells

cells with an incorrect number of chromosomes

cancer is a common result in cells that what

lose the ability to correct errors in DNA replication + to prevent mitosis w/ checkpoints

which is slower asexual or sexual reproduction?

sexual reproduction