Chapter 10 - Mendel, Genes, inheritance

Question 1

Theory of inheritance

Answer 1

The Chromosomal Theory of Inheritance identified chromosomes as the genetic material responsible for Mendelian inheritance.

Question 2

Mendels first hypothesis

Answer 2

• Traits for characters occur in pairs

- Diploid: two copies of each chromosome and hence each gene on the chromosome

Question 3

Mendels second hypothesis

Answer 3

If two traits are different, one trait is dominant over the other

• Dominant trait is expressed
• Recessive trait is masked

Question 4

Mendel third hypothesis

Answer 4

Two traits separate and enter gametes singly

- Two gametes fuse together to produce a zygote that contains two traits

Question 5

Homozygous

Answer 5

Both alleles are the same: PP or pp

Question 6

Heterozygous

Answer 6

Two different alleles: Pp

Question 7

Genotype

Answer 7

Genetic constitution of an organism

- PP, Pp, pp

Question 8

Phenotype

Answer 8

The physical characteristics

Question 9

Tetra cross

Answer 9

A cross between an individual with the dominant phenotype and a homozygous recessive indivudual

Question 10

How can you tell if an individual is a homozygous or heterozygous ?

Answer 10

A test cross can be conducted to determine the alleles present in the genotype

Question 11

Principle of independent assortment

Answer 11

Traits that govern two different characters segregate independently during formation of gametes

• We know this is due to independent assortment and crossing over during meiosis

Question 12

In terms of Mendelian genetics, what is a carrier?

Answer 12

A heterozygote individual that could unknowingly pass on a recessive allele.

Question 13

What is an autosomal trait?

Answer 13

An autosomal trait is a trait that is coded by a gene on an autosomal chromosome with equal copies of it. An autosomal chromosome is not a sex chromosome.

Question 14

Difference between a Dominant and recessive autosomal trait?

Answer 14

In dominant disorders, the dominant member of the gene pair controls how the gene activities are expressed, so the other gene can carry the same or normal information. In recessive disorders, the normal gene compensates for the bad information in the other

Question 15

Alibinism

Answer 15

he genetically inherited condition in which there is a marked deficiency of pigmentation in skin, hair, and eyes. An individual with these traits is an “albino.” Since the gene for albinism is recessive, it only shows up in the phenotype of homozygous recessive people. This is a pleiotropic trait.

Question 16

Alleles

Answer 16

alternate forms or varieties of a gene. The alleles for a trait occupy the same locus or position on homologous chromosomes and thus govern the same trait. However, because they are different, their action may result in different expressions of that trait.

Question 17

Carrier

Answer 17

an individual who is heterozygous for a trait that only shows up in the phenotype of those who are homozygous recessive. Carriers often do not show any signs of the trait but can pass it on to their offspring. This is the case with hemophilia.

Question 18

Codominance

Answer 18

the situation in which two different alleles for a trait are expressed unblended in the phenotype of heterozygous individuals. Neither allele is dominant or recessive, so that both appear in the phenotype or influence it. Type AB blood is an example. Such traits are said to be codominant.

Question 19

F1 generation

Answer 19

he first offspring (or filial) generation. The next and subsequent generations are referred to as f2, f3, etc.

Question 20

Homologous Chromosomes

Answer 20

chromosomes that are paired during the production of of sex cells in meiosis. Such chromosomes are alike with regard to size and also position of the centromere. They also have the same genes, but not necessarily the same alleles, at the same locus or location.

Question 21

Zygote

Answer 21

a “fertilized” ovum. More precisely, this is a cell that is formed when a sperm and an ovum combine their chromosomes at conception. A zygote contains the full complement of chromosomes (in humans 46) and has the potential of developing into an entire organism.