TOPIC 2C 2 PATTERNS OF INHERITENCE

What is a phenotype ?

1. It is the physical and chemical characteristics that make up the appearance of the organism.

2. Examples include size of an olive, color of a flower.

What is a genotype ?

1. It is the combination of alleles that partially affect the genotype.

What are the causes of differences in genotypes between individuals ?

1. Rearrangements of genes during meiosis.

2. Inheritance of genes from two different individuals in sexual reproduction.

What is a homologous pair ?

1. It is two sets of chromosomes which are arranged into matching pairs.

What is a gene locus ?

1. A gene locus is a specific site of the gene for a specific feature.

Each gene is a different segment of a DNA for a particular protein, true or false ?

1. True.

The chromosomes in a homologous pair carry the same genes, except ?

1. The sex chromosomes.

The gene for a specific characteristic is always found on the same position on the chromosome, true or false ?

1. True.

What is an allele?

1. An allele is the slightly different version of a gene that codes for a phenotype.

What is homozygous?

1. It is when the two alleles for the specific phenotype are identical.

What is heterozygous ?

1. It is when the two alleles that code for the phenotype are different.

Some phenotypes are dominant, what does that mean ?

1. Their effect is always shown, whether the individual is heterozygous or homozygous.

2. Even if one recessive allele is present.

What is a recessive phenotype ?

1. It is an allele that is only expressed when the individual is homozygous.

Why are homozygotes referred to as true breeding ?

1. This is because if your cross bred two homozygous individuals, all their offspring will express the phenotype that their parents have.

When genes are considered individually in a genetic cross, what is it called ?

1. Monohybrid cross.

What is test cross, and what is it used for ?

1. Test cross is when the crop is cross bred with a homozygous recessive individual.

2. This is to see whether the crop is homozygous for the desired feature.

3. If it is not, the offspring will express features of the other allele.

What is codominance ?

1. Codominance is when two phenotypes are expressed at the same time, while both alleles are present.

How do are blood types determined by the alleles ?

1. Blood types are categorized by the antigens on the surface of the red blood cells.

2. Type A has type A antigens,

3. Type B has type B antigens,

4. Type AB has both A and B antigens,

5. Type O has no antigens.

How does an AB blood type work ?

1. It works as if there is both individually A and individually B antigens in the erythrocytes.

2. There is no blending of phenotypes.

What features should an organism have for it to be suitable for carry out genetic experiments ?

1. Be relatively easy and cheap to grow

2. Have a short life cycle

3. Produce large numbers of offspring

4. Have clear, easily distinguishable characteristics

Why aren’t the ratios seen in genetic cross seen in real life ?

1. Preproduction is a result of chance, the combination of alleles in each gamete is completely Random and so is the joining of particular gametes.

2. Some offspring die before being sampled. Miscarriage

3. Inefficient sampling techniques