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biology > topic ten > Flashcards

topic ten Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is synpasis

A

the pairing of homologous chromosomes in prophase of mitosis

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2
Q

what condenses in prophase of mitosis

A

each replicated chromosome (consisting of two identical sister chromatids connected at the centromere) condenses completely and independently

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3
Q

what are the resulting paris of condensd chromosomes called

A

tetrads (referring to the four chromatids) or bivalents (referring to the two chromosomes)

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4
Q

Tetrad formation during prophase I of meiosis. the condemning of chromosomes visual representation

A
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5
Q

do sister chromatids have the same alleles

A

yes as well as the same genes, as they are identical copies produced during replication

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6
Q

what does crossing over involve

A

Crossing over begins by breaking a covalent bond in the backbone of both strands of the DNA double helix at identical positions on the non-sister chromatids and then causing the helices to switch sides. The position of the chromatids are switched so that, when the backbones are healed (ligated), a chromatid is covalently bonded to the non-sister chromatid.

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7
Q

what is chiasma

A

The point of exchange between the two non-sister chromatids creates an X-shaped connection

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8
Q

result of crossing over

A

the exchange of alleles between non sister chromatids. greatly increases genetic diversity present in the gametes at the end of meiosis

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9
Q

What is the term for the point of attachment between sister chromatids in a tetrad?

A

centromere

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10
Q

waht is the point of attachment between non-sister homologous chromatids that will persist until homologues are separated in anaphase I.

A

chiasma

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11
Q

why does independent assortment occur

A

because during metaphase I of meiosis, tetrads (pairs of homologous chromosomes) line up on the equatorial plate with random orientation

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12
Q

how many possible orientations are there for a tetrad

A

two as they culd be pulled to one of two poles

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13
Q

waht are Gametes containing a new combination of alleles, different from the two parents called

A

recombinant gametes

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14
Q

Genes that are far enough apart on the same chromosome show

A

independent assortment

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15
Q

does mitosis or meirosis produce geneticlaly identical cells

A

mitosis

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16
Q

mitosis and meiosis are both preceeded by the same…

A

cell cycle

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17
Q

what are the three events that all contribute to genetic diversity in meiosis I

A

prophase I: crossing over
metaphase I: random orientation of tetrads
anaphase I: reduction division

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18
Q

how does reduction division contribute to genetic diversity

A

Reduction division from the diploid to the haploid number of chromosomes in the nucleus, as a result of homologous chromosomes moving to opposite poles. When the gametes fuse and combine the DNA from two genetically different parents, the resulting offspring possesses the standard diploid number of chromosomes.

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19
Q

Independent assortment of chromosomes is a result of:

A

The random and independent way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I.

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20
Q

homoloogus chromosomes seperate in _______, while sister chromatids separate in _______

A

meiosis I,
meiosis iII

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21
Q

what is the F2 phenotypic ratio for a dihybrid cross between two heterozygous parents if the two genes involved are unlinked and show independent assortment

A

9:3:3:1

22
Q

what are linked genes

A

genes found on the same chromosome

23
Q

why will the ratio of observed offspring not match the punnet square predictions if closely linked genes are used

A

it assumes independent assortment

24
Q

Several genes (two or more) on the same chromosome that do not show independent assortment are called

A

a linkage group

25
Q

the closer the loci of two linekd genes,

A

the less frequently they are seperated by crossing over

26
Q

non mendelian ratios can be due to

A

sex linkage (any gene on sex chromosomes)
or
autosomal linkage (two genes found on the same autosomal chromosome)

27
Q

when genes are linked, special notation is used. to show dominance, a capital letter, or letters if the organism is drosophilia, is used.

what do the horizontal lines represent

A

The horizontal lines represent the homologous chromosomes, with one allele for each gene. The alleles for a gene are shown as a vertical pair, indicating the locus of the gene.

28
Q

waht is the easieset way to test fo rlinkage between two genes

A

use a test cross, where a heterozygous parent is crossed with a homozygous recessive parent.

29
Q

How would you explain a test cross involving dihybrid flies in which parental-type offspring and small numbers of new combinations of parental phenotypes are produced?

A

The two genes are linked on the same chromosome and crossing over has occurred.

30
Q

what is a gene pool

A

consists of all the genes and their different alleles present in an interbreeding population.

31
Q

what is allele frequency

A

usually expressed as a percentage or proportion, measures how common an allele is in a population.

32
Q

how is the depth or richness of the gene pool measured

A

by the number of alleles and their relative freqencies

33
Q

what is a species

A

a group of organisms that can interbreed to produce fertile offspring (this definition) can only be used with sexually reproducing species)

34
Q

random fluctuations in allele frequency are known as

A

genetic drift

35
Q

what is the original source of all genetic variations

A

mutations in dna

36
Q

selective pressure can have three effects on phenotype,

A
37
Q

stablising selection

A

acts against extremes of a trait

38
Q

directional selection

A

acts when one extreme of a trait offers a survival or reproductive advantage

39
Q

disruptive selection

A

most frequent phenotype becomes a disadvantage and extremes have better survival and reproductive rates

40
Q

speciation

A

involves the formation of one or more new species from an ancestral species. Production of two or more new species occurs due to reproductive isolation between populations.

41
Q

reproductive isolation

A

the failure of individuals from two populations to mate and produce fertile offspring, resulting in the reduction or elimination of gene flow between the populations.

42
Q

allopatric speciation

A

When a new species emerges during geographic separation of a population from other populations

43
Q

geographic isolation

A

the separation of populations by a physical barrier that reduces or prevents gene flow.

44
Q

behavioural isolation

A

any behaviour that acts to reduce or eliminate gene flow between portions of a population, such as variations in courtship song or location.

45
Q

sympatric speciation

A

when a portion of a population develops into a new species while still living in the same geographic area as the ancestral population. Sympatric speciation can occur due to behavioural, temporal, or other forms of speciation.

46
Q

temporal isolation

A

any shift in the timing of a behaviour that acts to reduce or eliminate gene flow between portions of a population.

47
Q

gradualism

A

occurs when major changes are the cumulative product of slow but continuous minor changes.

48
Q

punctuated equilibrium

A

implies long periods without appreciable change and short periods of rapid evolution.

49
Q

compare gradualism and punctuated equilibrium

A
50
Q

polyploidy

A

refers to the presence of more than two complete sets of chromosomes in a cell.

51
Q
A

biology (13 decks)

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