Unit 10 Flashcards

Question

Distinguish between metaphase one and two

Answer 1

Homologus chromosomes separate in meiosis one while sister chromatids separate in meiosis two

Answer 2

Independent assortment of genes is due to the random orientation of pairs of homologous chromosomes in meiosis one Independent assortment only occurs with unlinked gene because linked genes that are present on the same chromosome will be inherited together

Answer 3

Genes loci Are said to be linked if on the same chromosome Unlinked genes are on different chromosomes and segregate independently as a result of meiosis

Answer 4

Variation can be discrete or continuous example discrete will be flower colour it can only be red or purple or continuous for example human height. The phenotypes of polygenic characteristics tend to show continuous variation. Polygenic traits such as human height may also be influenced by the environmental factors.

Answer 5

His breeding experiments involving fruit files clearly demonstrated the linked genes were not independently assorted. Sex linked: -he discovered a clear sex bias in phenotypic distributions in white eyed mutants Gene linkage: -certain phenotypes of combinations occurred in much lower frequencies than was to be expected -Gene linkage occurred and hence did not independently assort -Linked alleles could be uncouple via recombination (crossing over) to create alternative phenotypic combinations These new phenotypes would occur at a much lower frequency Cross over frequency: -Genes with a higher crossover frequency are further apart -Genes with a lower crossover frequency are close together -developed the first gene linkage maps that show the relative position of genes on a chromosome

Answer 6

Example human height may also be influenced by environmental factors -The added affect of environmental pressures functions to increase the variation seen for a particular trait -human height is controlled by multiple genes resulting in a bell shaped spectrum of potential phenotypes -environmental factors such as diet and health or disease can further influence an individual humans height Example of human skin colour -Skin colour is controlled by multiple melanin producing genes but is also affected by factors such as sun exposure

Answer 7

Recombinance final types can be identified by performing a test cross -Linked genes become separated by a chiasma there will be an exchange of alleles between the nonsister chromatids create new allele combination that are different to those of the parent -The frequency of recombinant phenotype is within a population will typically be lower than that of non-recombinant phenotypes -crossing over is a random process and chiasmata do not form at the same locations with every meiotic division - relative frequency of recombinant phenotypes will be dependent on the distance between linked genes - Greater when the genes are further apart on the chromosome

Answer 8

Alleles are usually shown side-by-side in a dihybrid crosses for example TTBB. In representing crosses involving linkage it is more common to show them as vertical pairs

Answer 9

A gene pool consists of all the genes and there are different alleles present in an interbreeding population. Large Gene pool = high amounts of genetic diversity Small gene pool = low amounts of genetic diversity Gene pools can be used to determine allele frequency

Answer 10

Evolution requires that allele frequencies change with time in populations in ways like: - mutation - gene flow: The movement of alleles into or out of a population as a result of immigration or emigration -Sexual reproduction -Natural selection

Answer 11

Reproductive isolation as whenever your province two populations for interbreeding (keeping their gene pool separate)

Answer 12

Occurs when two populations differ in their periods of activity or reproductive cycles -e.g. Leopard frogs and wood frogs reach sexual maturity a different times in the spring

Answer 13

Occurs when two populations exhibit two different specific courtship patterns -e.g. Certain populations of crickets may be morphologically identical but only respond to Specific mating songs

Answer 14

Occurs when two populations occupy different habitats or separate niches within a common region -e.g. lions and tigers occupy different habitats and do not interbreed (usually)

Answer 15

Position due to divergence of isolated populations can be gradual. -Allopatric and sympataric position results in gradualism -position is seen as a smooth and continuous process (Big changes results from many cumulative small changes) -supported by the fossil record of the horse with many intermediate forums connecting the ancestral species to the modern equivalent Specialisation can occur abruptly -Punctuated equilibrium suggests that species remain stable for long periods before undergoing abrupt and rapid change

Answer 16

-an intermediate phenotype is favoured at the expense of both phenotypic extremes -e.g. Human birth weights (too large = birthing complications; too small=risk of infant mortality)

Answer 17

- One phenotypic extremist selected at the cost of the other phenotypic extreme - e.g. Development of antibiotic resistance in bacterial populations

Answer 18

-both phenotypic extremes are favoured at the expense of the intermediate phenotypic ranges -e.g. The proliferation of black or white moths in the regions of sharply contrasting colour extremes

Answer 19

Polyploidy is an offspring have additional sets of chromosomes Sympatric Speciation will result if Polyploid offspring are viable and fertile but cannot interbreed with the original parent population Examples: Triploid (3n) = ~ 24 chromosomes (e.g. Allium carinatum- keeld garlic) Tetraploid (4n) = ~32 chromosomes (e.g. Allium tuberosum - Chinese chives)

Answer 20

Non-disjunction - failure of chromosome Paris to separate during meiosis Diploid gamete - can lead to polyploidy Fusion of diploid and haploid gamete produces as triploid cells Unable to produce Viable Gametes during meiosis

Answer 21

Increased stability of bivalence at chiasmata Increase genetic variability (if crossing over occurs )

Answer 22

The process of crossing over results in the exchange of DNA between the maternal and paternal chromosomes. Crossing over can decouple Linked Combinations of alleles and therefore lead to independent assortment . Furthermore crossing over can occur multiple times and between different chromatids within the same, Homologous pair

Answer 23

In melosis l sister chromatids remain associated with each other the homologues chromosomes behaved in a coordinated fashion in prophase. - homologus chromosomes exchange DNA leading to genetic recombination and meiosis l is a reduction division in that it reduces the chromosome number by half -The process that results in the creation of genetic variety of gametes are initiated in meiosis l -The segregation of homologous chromosomes occurs during anaphase l resulting in two haploid cells each with only one copy of each homologous pair

Answer 24

William Bateson and Reginald Punnett conducted crosses with sweet peas One of the parents cells long pollen(LL) and purple flowers (pp) The other had round pollen (ll) and red flowers(pp) The surprising results came in the F (2)generation of a dihybrid cross Instead of the expected ratio of 9:3:3:1, there was four more of the individuals with the paternal phenotype seen in the P generation Insert smaller number of the non-paternal phenotypes known as recombinants

Unit 10 Flashcards

(48 cards)