BIO 1109 Lecture 14: Biology class 14 notes

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18 Oct 2015

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Transfer of characteristics from one generation to the next. Paired alleles at a gene location on homologous chromosomes are the same. Paired alleles at a gene location on homologous chromosomes are different. Stronger code which is always expressed in the heterozygous state. Use a capital letter to represent e. g. f=freckles w=widow"s peak hairline. Use a lower letter to represent e. g. f=no freckles. Use 2 letter e. g. ff or ff or ff. Principle of segregation allele pairs separate when egg or sperm are formed because homologous pairs of chromosomes separate during meiosis. Punnett squares used to predict result of genetic cross in offspring i. e. what could kids look like. Monohybrid cross predict offspring (f1 generation) considering one characteristic of parents (p generation) Brown eyes are usually dominant over blue eyes. Suppose a blue-eyed man marries a brown-eyed woman whose father was blue eyed. What % of their children would you predict will have blue eyes.

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.

QUESTION 1

Jim is blood type A, his brother John is type O and his sister Jane is type AB. What are the genotypes of their parents?

Which of the following is true for alleles that show incomplete dominance?

Heterozygotes have a genotype like the dominant allele.

Homozygotes have a genotype like the recessive allele.

Heterozygotes have a phenotype intermediate between the dominant and recessive alleles.

Homozygotes have the same phenotype as the heterozygotes.

QUESTION 3

Which principle of inheritance concluded that when games are formed in meiosis, the two alleles of each gene separate from one another, and each gamete receives only one allele?

independent assortment

Which term best describes a condition in which alleles at one locus can alter the expression of alleles at another locus?

polygenic inheritance

A single unit of genetic information located on a chromosome defines:

The physical expression (appearance or function) of an organism's genes defines:

genotype

a single characteristic

Palomino horses (golden color with a blond mane) are an incompletely dominant trait produced by the combination of the chestnut color allele and the cream color allele. If you wanted to produce as many palominos as possible, which mating strategy below would be the best choice?

Which term best describes the effect of a single gene on multiple aspects of the phenotype?

polygenic inheritance

QUESTION 9

Which term best describes the separate expression of both alleles for a single trait in the same cell?

polygenic inheritance

QUESTION 10

One form of a gene found on a single chromosome defines:

A chocolate lab (whose mother was a yellow lab) is mated with a black lab whose genotype is BbEe. What fraction of the offspring would be expected to be yellow labs?

What type of allele is always expressed regardless of whether the individual is homozygous or heterozygous for it?

Both the dominant and recessive alleles

Given the parents AABBGgHhrr Ã AabbGgHhRr, assume simple dominance and independent assortment. What proportion of the progeny will be expected to have the genotype AaBbggHHrr?

___________________ is defined as having two of the same type of allele for a particular trait.

The physical position of an allele on a single chromosome defines:

Which term best describes two or more genes affecting the phenotype in an additive fashion?

codominance

polygenic inheritance

Sometimes one gene may have the effect of suppressing an abnormal (mutant) allele of another gene, resulting in the normal phenotype. Flies that are homozygous for the mutant gene, suppressor or hairy wing (s/s) will have a normal phenotype if they are also homozygous for the mutant gene, hairy wing (h/h). The following questions refer to the offspring ratios after the mating of individuals heterozygous for the wild type and mutant alleles of BOTH suppressor of hairy wing (s⁺/s) and hairy wing (h⁺/h) genes. The genes, s⁺ and h⁺ are located on separate chromosomes. Use the symbols s^D, s^R, h^D, and h^R to denote the genotype of a fly that is heterozygous for:

A. Dominant (D) mutations in both s⁺ and h⁺

B. Recessive (R) mutations in both s⁺ and h⁺

i. What phenotypic ratio of offspring would you expect if suppression occurs when you sib-mate flies heterozygous for dominant mutations in both s⁺ and h⁺ ?

ii. What phenotypic ratio of offspring would you expect if suppression occurs when you sib-mate flies heterozygous for recessive mutations in both s⁺ and h⁺ ?

iii. Draw the punnett squares showing both the genotype and corresponding phenotype for EACH of the 16 outcomes for both scenarios.

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BIO 1109 Lecture 14: Biology class 14 notes

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