BIO 101 Lecture Notes - Lecture 10: Albinism, Y Chromosome, Scrotum

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lilacbear269

18 Aug 2016

School

Quinnipiac University

Department

Biology

Course

BIO 101

Professor

Carleton

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Document Summary

Genes: sequences of nucleotides at specific locations on chromosomes: homologous chromosomes carry the same kinds of genes for the same characteristics, genes for the same characteristic are found on the same loci on both chromosomes. Loci: specific location or position of a gene and dna sequence on a chromosome: genes for a characteristic found on homologous chromosomes may not be identical, alleles: alternative versions of genes found at the same gene locus. There are two on each member of homologous chromosome. Can be the same blue/blue eyes can be different brown/blue eyes. Gregor mendel: father of modern genetics, austrian monk, transmission of characteristics from one to another. He was able to find without knowing anything like the scientific method or inquiry even. Mendels crosses : cross of pea plans true-breeding for white or purple flowers. Parental generation (p) cross-fertilization of a purple and white flower. First generation offspring (f1) purple flowered plants: self-fertilization of f1 pea plants with purple flowers.

Related Questions

These all relate to exceptions to the inheritance patterns encountered by Mendel.â

Why do multiple and lethal alleles often result in modifications of the classic Mendelian monohybrid and dihybrid ratios?

Select the four correct statements.

-When an essential gene is mutated, it can result in a lethal phenotype. There are no classic Mendelian monohybrid and dihybrid ratios.

-In the case of codominance, heterozygotes produce gene products from both alleles of a gene. Classic Mendelian monohybrid and dihybrid ratios are modified by codominance.

-In the case of incomplete dominance, the phenotype of the heterozygote is distinct from and often intermediate to the phenotypes of homozygous individuals. Classic Mendelian monohybrid and dihybrid ratios are modified by incomplete dominance.

-Genes exist in a large number of allelic versions and a diploid organism has two homologous gene loci that may be occupied by different alleles of the same gene. This can result in many different phenotypes for traits, which may not follow typical Mendelian ratios.

-When an essential gene is mutated, it can result in a lethal phenotype. This results in a modification of classic Mendelian ratios.

-The phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygous genotypes. The joint expression of both alleles in a heterozygote is called codominance. There are no classic Mendelian monohybrid and dihybrid ratios.

-Genes exist in a large number of allelic versions, but in a diploid organism, only one allele of the gene can occupy one homologous gene loci. Classic Mendelian inheritance cannot explain this phenomenon.

-Each gene produces a unique gene product. The effect of one allele in a heterozygote completely masks the effect of the other. Classic Mendelian genetics cannot explain this phenomenon.

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

coralox210

Ants are haplodiploid organisms. This means females are diploid (2n) and males are haploid (n). The gametes produced by both males and females are haploid (n). There is no homologous recombination in males during gamete formation. There is no sex chromosome.

In an ant species, it is known that wings formation (F) and setae density (D) are each controlled by a different, simple-Mendelian locus/gene. Individuals which are homozygous recessive for both genes have no wings (f) and no setae (d). Previous experiments also indicated that both loci/genes are on the same chromosome.

a. Design a test cross to map the genetic distance of the genes, by writing the genotype of the tester and its mate. (2 pts)

Genotype of tester:

Genotype of testerâs mate:

b.In order for the test cross to produce offspring with non-parental phenotypes, the tester has to be of a specific sex. What sex must the tester be? Briefly explain your choice in your own words. (Hint:what is a test cross?) (2 pts)

Sex of tester:

emeraldweasel173

BIO 101 Lecture Notes - Lecture 10: Albinism, Y Chromosome, Scrotum

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