2.3 variation and sexual reproduction

Question 1

what environmental factors, other than temperature, can be used to determine the sex of an organism?

Answer 1

size, parasitic infection, competition

Question 2

where is TSD most prevalent?

Answer 2

in reptiles

Question 3

what is TSD?

Answer 3

where the temperature experienced during the incubation period of the embryo determines its sex

Question 4

what is the main benefit of being a hermaphrodite?

Answer 4

their mate does not have to be of the opposite sex if they are struggling to find one

Question 5

do hermaphrodites have partners to exchange gametes with

Answer 5

yes usually

Question 6

what is a hermaphrodite?

Answer 6

a species that has both male and female reproductive organs, so can produce both types of gametes

Question 7

what does x inactivation leave

Answer 7

only one active x chromosome in each cell of the female embryo

Question 8

what does x inactivation mean for carriers?

Answer 8

they are less likes to be affected by deleterious mutations on the x chromosomes

Question 9

what are two qualities of x inactivation

Answer 9

random in each cell
irreversible

Question 10

what does x-inactivation prevent

Answer 10

female from presenting double the quantity of x linked gene products which could be harmful to cells

Question 11

what happens during x inactivation

Answer 11

during embryonic development of every female, most of one of the two X chromosomes in each cell inactivates

Question 12

what does heterogametic mean

Answer 12

females produce gametes with two possible combinations of chromosomes

Question 13

what does homogametic mean

Answer 13

females produce gametes with the same combination of chromosomes

Question 14

a male has a recessive allele on one X chromosome…

Answer 14

which has no copy to mask its effects

Question 15

a female has a recessive allele on one X chromosome…

Answer 15

which can be masked by a dominant allele on the other X

Question 16

what is the root cause of the pattern of inheritance called sex linkage?

Answer 16

the Y chromosome lacks many genes found on its homologous x chromosome

Question 17

why are x and y homologous?

Answer 17

they pair up during meiosis I

Question 18

what determines the development of male traits in most mammals?

Answer 18

the SRY gene on the Y chromosome

Question 19

what do sex chromosomes do?

Answer 19

determine whether an individual is male or female

Question 20

what are the four things we must remember about meiosis II?

Answer 20

single chromosomes line up at the equator
spindles contract and chromatids move to opposite poles
cytokinesis occurs
4 non-identical haploid gametes

Question 21

what does a greater distance between linked genes mean?

Answer 21

there is a greater chances of crossing over, resulting in greater frequency of allele recombination

Question 22

what are linked genes?

Answer 22

genes on the same chromosome

Question 23

what are linked genes?

Answer 23

genes on the same chromosome

Question 24

what does independent assortment result in?

Answer 24

the production of gametes with varying combinations of maternal and paternal chromosomes

Question 25

how does meiosis I end?

Answer 25

cytokinesis occurs and two daughter cells are formed

Question 26

what happens fourth in meiosis I?

Answer 26

spindles contract and each homologous partner moves to opposite poles of the cell

Question 27

what is independent assortment?

Answer 27

homologous chromosomes line up at the equator independent of maternal and paternal origin

Question 28

what does crossing over result in?

Answer 28

recombination of alleles as info is shared between linked genes

Question 29

what happens third in meiosis I?

Answer 29

homologous chromosomes line up at the equator and independent assortment occurs

Question 30

what happens second in meiosis I?

Answer 30

chiasmata form at points of contact between non-sister chromatids and crossing over occurs

Question 31

what begins meiosis I?

Answer 31

chromosomes condense and homologous chromosomes pair up

Question 32

does meiosis occur in asexual reproduction?

Answer 32

no

Question 33

what are two examples of cells that undergo horizontal gene transfer?

Answer 33

bacteria and yeast cells (prokaryotes)

Question 34

what does horizontal gene transfer allow for?

Answer 34

gene transfer between individuals = increased variation and faster evolutionary change

Question 35

in which organisms can horizontal gene transfer occur?

Answer 35

asexually reproducing organisms

Question 36

what allows for natural selection and evolution to take place in asexually reproducing populations?

Answer 36

mutations can sometimes occur that allow for small degrees of variation

Question 37

where is parthenogenesis more common?

Answer 37

cooler climates with low parasite density

Question 38

what is parthenogenesis?

Answer 38

reproduction from a female gamete without fertilisation.

Question 39

what are examples of asexual reproduction in eukaryotes include?

Answer 39

vegetative cloning in plants parthenogenesis in lower plants and animals

Question 40

asexual reproduction involves one parent producing daughter cells - what does this allow?

Answer 40

an unlimited colony to be produced over time

Question 41

when can asexual reproduction be a particularly successful reproductive strategy?

Answer 41

in narrow, stable niches recolonising disturbed habitats

Question 42

why does sexual reproduction remain the main reproductive method used?

Answer 42

the benefit of increased genetic variation outweighs the costs

Question 43

why is genetic variation vital?

Answer 43

provides the raw material required for adaptation reduces the chance of parasitic infection

Question 44

what is the cost of asexual reproduction?

Answer 44

no variation

Question 45

what is the benefit of sexual reproduction?

Answer 45

variation = fundamental to evolution

Question 46

what are the costs of sexual reproduction?

Answer 46

males are unable to produce offspring only half of each parent's genome is passed on disrupts successful genomes

Question 47

what are the benefits of asexual reproduction?

Answer 47

time-efficient less energy required only 1 parent required increased number of offspring regularly

Question 48

what is asexual reproduction?

Answer 48

a mode of reproduction by which offspring arise from a single organism and inherit the genes from that parent only

Question 49

what are 2 problems arising from heterogametic males and homogametic females

Answer 49

males and females will have different inheritance patterns female has a potential double dose effect from the 2 copies of the non-homologous section

Question 50

what is sexual reproduction?

Answer 50

the production of new living organisms by combining genetic information from individuals of different types