Chapter 10 - Mendel, Genes, inheritance Flashcards
Theory of inheritance
The Chromosomal Theory of Inheritance identified chromosomes as the genetic material responsible for Mendelian inheritance.
Mendels first hypothesis
- Traits for characters occur in pairs
- Diploid: two copies of each chromosome and hence each gene on the chromosome
Mendels second hypothesis
If two traits are different, one trait is dominant over the other
- Dominant trait is expressed
- Recessive trait is masked
Mendel third hypothesis
Two traits separate and enter gametes singly
- Two gametes fuse together to produce a zygote that contains two traits
Homozygous
Both alleles are the same: PP or pp
Heterozygous
Two different alleles: Pp
Genotype
Genetic constitution of an organism
- PP, Pp, pp
Phenotype
The physical characteristics
Tetra cross
A cross between an individual with the dominant phenotype and a homozygous recessive indivudual
How can you tell if an individual is a homozygous or heterozygous ?
A test cross can be conducted to determine the alleles present in the genotype
Principle of independent assortment
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
In terms of Mendelian genetics, what is a carrier?
A heterozygote individual that could unknowingly pass on a recessive allele.
What is an autosomal trait?
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.
Difference between a Dominant and recessive autosomal trait?
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
Alibinism
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.
Alleles
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.
Carrier
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.
Codominance
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.
F1 generation
he first offspring (or filial) generation. The next and subsequent generations are referred to as f2, f3, etc.
Homologous Chromosomes
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.
Zygote
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.
