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BIOSC-116 Lecture Notes - Lecture 11: Secondary Sex Characteristic, Allosome, Y Chromosome

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coppermule660
16 Jun 2020
School
Diablo Valley College
Department
Biological Science
Course
BIOSC-116
Professor
Khan

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Document Summary

Codominance ex: a and b blood types. Alleles: ia and ib which are co-dominant. Allele i which is recessive to the other 2 alleles. If you have the a allele and the b allele is means that they are equally expressed and you"ll have both the a and b markers are on your blood cell co dominance. A gene has more than 2 alleles present in a population. Ex: the abo blood group gene has 3 possible alleles: ia , ib and i. There are only 2 alleles present in every individual but there are 3 possible alleles that you could be selecting from. Help to determine the sex of the individual. Both have genes on them to control the development of secondary sexual characteristics (puberty) But also carry genes that are unrelated to sexual development. Sex chromosomes are not truly homologous, but they do pair up during meiosis. X chromosomes is larger than the y.

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Related Questions

With respect to genetics, ABO blood types are controlled by asingle gene designated I, which has three alleles. The I A allelegives blood type A, I B gives blood type B, and i gives blood typeO. The I A and I B alleles are codominant and i allele is recessiveto both the I A and I B alleles.

Aside from the I alleles, there are two other genes that whenmutated affect ABO blood type inheritance. The first mutant isrecessive to wild type and is designated x. A homozygous xxindividual is phenotypically O for blood type no matter what thegenotype is of the I gene. For example, I A /I A x/x or I B /I Bx/x individuals are O type. The second mutant, is dominant to thewild type Y allele and is designated Yd . An individual carrying aYd allele is phenotypically blood type O no matter what thegenotype is of the I gene. For example, an I A /I A Y/Yd or I B /IB Y/Yd individuals is O.

a. Propose a biochemical model that explains the O phenotype ofthe recessive homozygous xx individual? Your model should explainthe biochemical function of the X gene in a wild type individualand should explain why the x mutation is recessive

Ploidy refers to the number of complete sets of chromosomes (genes) present in a cell. The number of chromosomes in a complete set is a fixed characteristic of a species. Humans are diploid with two sets of 23 chromosomes. Fruit flies are diploid with two sets of 4 chromosomes. Sexually reproducing organisms are diploid, each somatic cell of an organism has two complete sets ("di" is a prefix indicating 2.). To complete a life cycle and reproduce new members of a species, mating is required. Mating brings a donation from a male and a donation from a female together. However, if the male and female cells remain diploid, the fertilization will result in a tetraploid zygote. In general, these are not viable. A mechanism is needed to form special haploid cells, gametes. The diploid set is split precisely into two complete haploid sets. That mechanism is meiosis.

The complete set of chromosomes of a species is also the complete set of genes of a species, the genome. (Yes, there is a minor contribution from mitochondria and chloroplasts. Inheritance of this information is "cytoplasmic".)

Please answer the following questions:

1. How many chromosomes in a brain cell of a fruit fly? How many chromosomes are in a liver cell of a human? Explain both answers.

2. How many chromosomes are in a fruit fly unfertilized egg? How many chromosomes are in a human egg? Explain both answers.

3. Why is meiosis necessary for sexually reproducing organisms? How many chromosomes are in a human zygote? Relate the two answers.

4. What is a gene allele? Suppose there is a gene called "bingo" and it is present once in a complete haploid set. How many alleles of "bingo" does a diploid individual have? How many copies or versions of the gene "bingo" are present in a diploid individual?

5. Modern DNA sequencing clearly identifies alleles by showing the different DNA sequence of each allele. These alleles may be termed structural alleles (I coined the term for this problem.). Classical genetics only dealt with phenotypes or visible traits. As a result, alleles of genes were identified by functionality, usually normal or non-functional. Using your knowledge of gene structure and gene expression, postulate a relationship between structural alleles and functional alleles. (include relative amounts; more, less, or equal).

While working in a pathology lab, you are presented with an ovine blood sample (2n=54) that is suspected to have a genetic abnormality. You decide to karyotype the sample and diagnose trisomy 24.

1. Assume two hypothetical genes A and B are located on chromosomes 24 and 25 respectively. How many alleles for each gene will be present in the Primary oocyte, secondary oocyte and ovum that produced the animal with the abnormal karyotype indicated above – Provide answers for all possible scenarios.

2. Describe the number of autosomal chromosomes and chromatids in the Primary oocyte, Secondary oocyte and ovum that produced the animal with the abnormal karyotype indicated above – Provide answers for all possible scenarios

3. Another two hypothetical genes P and Q are located on chromosome 1; with the dominant alleles (P and Q) in coupling phase, and recessive alleles (p and q) in coupling phase on homologous chromosomes. Suppose a single crossing over occurs between the two genes during meiosis. What is the probability that the ovum that gave rise to karyotypically abnormal animal contains a chromatid with dominant alleles P and Q in coupling phase?

4. Suppose the animal had an XXY karyotype instead of trisomy 24. Did non-disjunction occur in the male or female parent (or both) and at which division(s), meiosis I or meiosis II?