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BSCI-1510L Lecture Notes - Lecture 8: Centimorgan, Mendelian Inheritance, Y Chromosome

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crimsonwalrus101
25 Apr 2016
School
Vanderbilt University
Department
Biological Sciences
Course
BSCI-1510L
Professor
Baskauf Steven

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Document Summary

In eukaryotic organisms, dna is present in structures calledchromosomes. Each chromosome consists of a single two-stranded dna molecule. Genes are located along the chromosomes and the position at which a particular gene is found is called a locus (plural: loci). In diploid organisms, each cell contains two sets of chromosomes. (do not confuse this with the two strands of dna within a single chromosome. ) The two versions of each kind of chromosome are calledhomologous chromosomes. This means that along their length both homologues have the same loci arranged in the same order. For example, humans have 23 kinds of chromosomes. Since two versions of each kind of chromosome are present, there are a total of 46 chromosomes in human cells (i. e. 2n=46). In normal cell division (mitosis), each of the chromosomes replicates before the cell divides. Each of the two daughter cells gets one copy of each chromosome. Thus each daughter cell is an exact duplicate of the parent.

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Related Questions

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.

Match the following definitions with the correct term. (We have not yet cover all of them in class, but you can find them in your reading.)


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A.

B.

C.

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E.

F.

G.

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I.

J.

K.

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A single mutation affects several traits.


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The frequency with which individuals of a given genotype manifest the mutant phenotype.


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B.

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A phenotypic trait whose expression depends on the additive effect of a number of genes.


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B.

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Expression of a gene is dependent on whether it has been inherited from the male or female parent.


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B.

C.

D.

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F.

G.

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Phenotypic effects on the offspring produced by the maternal genome.


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B.

C.

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E.

F.

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Genetic information transmitted by chloroplasts or mitochondria.


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B.

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F.

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The degree in which a phenotype for a given trait is expressed.


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B.

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Determines whether two mutations are at the same locus or different loci.


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B.

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G.

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Genetic differences that are due to alterations of the DNA that do not included changes in base sequence.


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B.

C.

D.

E.

F.

G.

H.

I.

J.

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L.

Characteristic determined by a gene on a sex chromosome.


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C.

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E.

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Characteristic encoded on an autosome that is more readily expressed in one sex.


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A gene at one locus that masks or suppresses the effect of a gene at a different locus.

A.

pleiotropy

B.

cytoplasmic inheritance

C.

epigenetics

D.

polygeneic inheritance

E.

imprinting

F.

sex-influenced trait

G.

sex-linked trait

H.

penetrance

I.

expressivity

J.

maternal effect

K.

complementation test

L.

epistasis

Answer the following Linked to sex genetics problems:

1.) In Drosophila the recessive mutation linked to the X chromosome, scalloped ( sd ), causes the edge of the wings to be irregular. Present the results (you must prepare the crossing scheme) phenotypic for F1 and F2 for a cross between:

A) female scallop and a normal male (regular edges)

B) A normal (homozygous) female and a scallop male .

C) Compare these results with those that would be obtained if scallop were an autosomal recessive mutation.

2.) In Drosophila the autosomal recessive ebony mutation (e) is located on chromosome 3 and produces a dark body in the fly that expresses it. What will be the phenotypic proportions for F1 and F2 that will be obtained from a cross between a scallop female and homozygous for a normal body, with an ebony male with normal wings? Solve by the bifurcated lines method.

3.) In Drosophila the recessive mutation linked to the vermilion X chromosome (v) produces bright red colored eyes in contrast to the wild phenotype that has brick red eyes. An autosomal recessive mutation, suppressor vermilion (su-v) causes homozygous or hemizygous males to females present vermilion red brick eyes. In the absence of the vermilion allele su-v has no effect on the phenotype of the eye. Determine the genotype and phenotype of F1 and F2 at a cross between a homozygous female for vermilion and su-v, with a vermilion male and wild homozygous for su-v (su-v + su-v + ) . Present the diagram of bifurcated lines for these crosses.

4.) At a crossroads with Drosophila involving recessive mutations white (linked to the X chromosome) and sepia (autosomal recessive) that produces dark eyes, predict the results of F1 and F2 when crossing pure parents with the following phenotypes.

A.) White females with sepia males.

B.) Sepia females with white males

5.) Two mothers have given birth to their children at the same time in an urban hospital with an excess of patients. The child of couple 1 has hemophilia, a condition caused by a recessive allele linked to the X chromosome. Neither parent has the condition. Couple 2 has a normal child even though the father is a hemophiliac. Several years later, couple 1 filed a lawsuit alleging that the babies were changed after birth and you are called to testify as a genetic counselor. What information would you give the jury in relation to the allegation of the couple 1?