BIS 2B Lecture Notes - Lecture 19: Inbreeding, Phenotype, Chromosome

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31 Jul 2018

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Answers to basic genetics study questions: mendel"s first law, the law of segregation: at any given genetic locus, each gamete randomly receives one of the two alleles carried by the parent. That is, the two alleles at a genetic locus within an individual segregate (separate) from one another during the process of gamete formation. Mendel figured this out when he noticed that phenotypic traits often disappeared during the f1 generation, only to reappear at predictable frequencies in the f2 generation. We now know that segregation occurs as a result of the separation of homologous chromosomes during meiosis: mendel"s second law, the law of independent assortment: each pair of alleles segregates independently of the alleles at other genetic loci. This is most likely to be true when genetic loci occur on different chromosomes, because chromosomes segregate independently of one another in.

Related Questions

Which of these statements is incorrect?

Syntenic genes are located on the same chromosome.

Independent assortment results in recombinant chromosomes.

You can reliably predict the relative genetic distance fromgenesâ physical distance on a chromosome.

Linked genes are always syntenic.

What is the relative genetic distance between two linked genesif the recombination frequency is 0.49?

0.49 cM

4.9 cM

49 cM

490 cM

What statement best explains the distortion in Mendelian ratiosobserved by Bateson & Punnett in 1905? (Reminder: they found anoverrepresentation of F2 offspring showing both dominant orrecessive phenotypes, and an underrepresentation of offspringdisplaying one dominant and one recessive phenotype)

Human error: they should have been more careful about theirexperimental setup.

Gene linkage: Genes for flower color and pollen shape arephysically close on the same chromosome, leading to a breakdown inthe independent assortment of the alleles for these traits.

Chromosome crossover: Homologous recombination of twochromatids during meiosis caused the alleles to shuffle, resultingin a breakdown of the independent assortment of the alleles forthose genes.

Random variation: No two situations are alike. In finitepopulations, you are going to get some variation across a mean.

When determining the relative genetic distance between twogenes, why is dihybrid back-cross preferable over traditionaldihybrid cross?

9:3:3:1 phenotypic ratio is easier to work with than 1:1:1:1ratio.

Genotypes of the offspring can be determined based on theirphenotype.

If the genes are independently assorted, the dihybrid back-crosswould result in only 2 genotypes in the F1 generation.

B and C

Why do we map genes?

To understand how genes interact with each other

Comparative genomics analysis

To determine the genotype of an organism

All of the above

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What is a genome? What is a genome made of? Describe the bacterial genome. How do bacteria reproduce? What is binary fission? Distinguish between a chromosome and chromatin. Where are chromosomes located in eukaryotic cells? What is the chromosome made of? What is a centromere? What is the centromere's role? What are sister chromatids and how do they arise? Distinguish between somatic cells and germ (gametes) cells. Describe the cell cycle. What are the different phases? What occurs during S phase? What is interphase? How is the cell cycle controlled?

Describe mitosis. What are the phases of mitosis? What occurs in each of the phases of mitosis? What is cytokinesis? How does this differ between plant and animal cells? What is a kinetochore? Where does it form? What is its role? What is the role of microtubules in mitosis? What is a centriole and what is it composed of? What is a centrosome and what is its role in mitosis? What is the metaphase plate and why is this important? What is the mitotic spindle, its role and its makeup? What defines a diploid cell? How many copies of each chromosome is in a diploid cell? What about a haploid cell? Why do the daughter cells of mitosis always have the same complement of chromosomes?

Describe meiosis. What are the phases of meiosis? What occurs in each of the phases of meiosis? Distinguish between meiosis I and meiosis II and describe how each of these processes compare to mitosis. Why do animal cells undergo meiosis? What is a gamete? What is a zygote? What are recombination, crossing-over, and chiasma? When and why does this occur? What is meant by 'homologous pair of chromosomes'? Why don't the daughter cells of meiosis have the same genetic makeup? What controls the segregation of chromosomes into the gametes?

What are genetic characters? What are genetic traits? What is an allele? What is a locus? How many alleles at each locus would a human cell have and why? Distinguish between genotype and phenotype. What is meant by a dominant gene? What is meant by a recessive gene? How do these differ? What is the genotype of a homozygous dominant organism? What is its phenotype? What is the genotype of a homozygous recessive organism? What is its phenotype? What is the genotype of a heterozygous organism? What is its phenotype? What is a genetic cross? Distinguish between the P, F1, and F2 generations. What is a true-breeding line? What is the genotype and phenotype of a cross between homozygous dominant and homozygous recessive parents? If the F1 progeny are crossed, what would be the genotype and phenotype of the F2 generation? What would be the phenotypic ratio? What would be the genotypic ratio? Be ready to generate Punnet square tests or probability analyses of crosses involving more than one genetic locus. Describe a dihybrid cross where two alleles are homozygous dominant in one parent and homozygous recessive in the other. What would be the phenotypic ratio of the F2 generation from this dihybrid cross? What is meant by independent assortment? Be prepared to calculate probabilities resulting from different crosses.

Distinguish between complete and incomplete dominance. How would incomplete dominance alter the results of a hybrid cross? What would the resulting F2 generation phenotype and genotype ratios be? What is codominance? How does this affect the results of crosses? Be prepared to determine likely blood types of parents based on the blood types of their offspring. What is a polygenic trait? What is a carrier state for a genetic disease? What is meant by linked genes? How does this affect expected outcomes of genetic crosses? How is gene linkage used for chromosomal mapping? Distinguish between autosomes and sex chromosomes. What sex chromosomes are found in women? What sex chromosomes are found in men? What are sex-linked traits? Be prepared to give the results of crosses that involve sex-linked recessive traits. What is the process of nondisjunction? What are the likely results? Why is this important? What is a Barr body? Recognize the genetic abnormality of Downs Syndrome, Turner's Syndrome, and Klinefelter's Syndrome.

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Question 1 Select one answer. 10 points Crossing over occurs:_______________.

during both meiosis I and meiosis II

during mitosis but not meiosis

during meiosis II only

during meiosis I only

Question 2 Select one answer. 10 points Homologous pairs ofchromosomes line up at the center of the cell in during which stageof meiosis?

Metaphase I,

Metaphase II,

Telophase I,

Telophase II

Question 3 Select one answer. 10 points A haploid organism hashow many copies of each chromosome?

1, 2, 3, 4

Question 4 Select one answer. 10 points The sister chromatidsseparate during which stage of meiosis?

Anaphase I, Anaphase II, Prophase I, Prophase II

Question 5 Select one answer. 10 points Describe the importanceof independent assortment: ________________________.

will assort independently of each other,

will sort to the same gamete,

are called alleles

All of these are true

Question 6 Select one answer. 10 points How many differentgametes are produced by a cell with the genotype AABb?

1, 2, 3,4

Question 7 Select one answer. 10 points The next two questionsare based on the following information. Part 1 of 2: In beansyellow (Y) is dominant to green (y) and smooth (S) is dominant towrinkled (s). What are the possible genotypes for the offspring ofthe following cross: YySS and YYSs.

Yy, SS, YY, Ss

YYSS, YySS, YYSs, YySs

YYSS, YYss, yySS, yyss

YS, yS, YS, yS

Question 8 Select one answer. 10 points Part 2 of 2: In beanswith yellow (Y) dominant to green (y) and smooth (S) dominant towrinkled (s): What are the phenotypes for the offspring in theexample in the previous question?

100% green wrinkled,

50% yellow smooth and 50% greensmooth,

100% yellow smooth,

50% yellow smooth and 50% yellowwrinkled

Question 9 Select one answer. 10 points Alleles are differentversions of a _______________.

chromosome,

genotype,

phenotype,

gene

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BIS 2B Lecture Notes - Lecture 19: Inbreeding, Phenotype, Chromosome

BIS 2B Full Course Notes

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