Section7:Inherited change Flashcards
What is a gamete?
An egg or sperm cell formed by meiosis and contains 23 single chromosomes.
What is a somatic cell?
A general term for body cells containing 46 chromosomes.
What is the definition of genotype?
Genotype is the genetic constitution of an organism
Genotype refers to the specific alleles present in an organism’s DNA.
What is the definition of phenotype?
Phenotype is the physical/observable characteristics of an organism which is determined by a combination of environment and genotype
Phenotype includes traits such as height, eye color, and behavior.
What is the key difference between a dominant and recessive allele?
A dominant allele only requires one copy to express itself in the phenotype
In contrast, a recessive allele requires two copies to be expressed.
What does co-dominant mean?
Two alleles contribute equally to the phenotype
Co-dominance is a form of inheritance where both alleles in a heterozygote are fully expressed.
Define monohybrid inheritance.
The inheritance of a single gene that causes a single characteristic
Monohybrid crosses typically involve one trait and can be analyzed using a Punnett square.
What is dihybrid inheritance?
The simultaneous inheritance of two characteristics
Dihybrid crosses consider two traits and can reveal the independent assortment of genes.
What is sex linkage?
When a gene controlling a particular characteristic is found on a sex chromosome
Sex-linked traits often exhibit different patterns of inheritance in males and females.
What is pure breeding?
When the genotype of each of the parents is homozygous
Pure breeding is essential for creating organisms that consistently express specific traits.
What are the steps to showing a genetic cross for an offspring?
- Parents phenotype
- Parents genotypes
- Parents gametes
- Genetic cross (F1)
- Genotype
- Phenotype
- Ratio
Why are the observed ratios of monohybrid/dihybrid inheritance often not the same as the expected ratio?
- Random fertilisation/fusion of gametes
- Population is small
- Selection advantage (survival)
What is the expected ratio for dihybrid inheritence?
9:3:3:1
What is it called when a gene has more than two alleles?
Multiple alleles
What is the best example of multiple alleles and describe each allele?
Human ABO blood group
* Allele I(A)=antigen A produced
* Allele I(B)=antigen B produced
* Allele I(O)=no antigens produced
A and B are co-dominant but O is recessive to both meaning it requires two alleles
Why is blood type O a universal doner and is given to people who’s blood type is unknown?
Allele I(O) produces no antigen this means that it is less likely to be rejected by the immune system of someone is who receiving a blood donation
What is sex-linkage?
When any gene is carried on the X or Y chromosome
Homologous
What is different between the X and Y chromosome?
The X chromosome is longer than the Y chromosome which means that most of the X chromosome length has no equivalent homologus proportion of the Y chromosome
Why are males more likely to have a recessive disease carried on the X chromosome?
There is no portion of the Y chromosome to posses the dominant allele
This also means that males cannot be carrier
What are autosomes?
Any chromosomes other than sex chromosomes
What are linked genes and how does it affect variation?
Linked genes are on the same chromosome and are passed into the same gamete and inherited tigethr
The loci of the genes are close together which means they will stay together during crossing over
This limits genetic variation
What inheritance pattern does autosomal linkage?
The mendelian inheritance is 1:3:3:1
What is epistasis?
This is when the allele of gene will express or masks the expression of another in the phenotype
