Genes B5 Flashcards
What are the characteristics of chromosomes?
Chromosomes are found in the nucleus. They are long coiled up molecules of DNA. Each chromosome contains a number of genes.
What is a genome?
A genome is all of an organisms genes combined.
What are the 2 factors which contribute to variation between organisms?
Genes and the environment.
What are phenotypes?
A phenotype is the characteristic that is seen (appearance). E.g. blue eyes.
What is a genotype?
A genotype is the genes that are present, e.g. Bb.
What is an allele?
An allele is the different forms of each gene, and we use capital and lowercase letters to show if alleles are dominant or recessive.
Describe the dominant and recessive alleles.
If two dominant alleles are present, e.g. BB, the dominant characteristic is seen e.g. brown eyes. If two recessive alleles are present, e.g. bb, the recessive characteristic is seen, e.g blue eyes. If one of each allele is present, e.g Bb, the dominant character is seen e.g brown eyes.
What is continuous variation?
Continuous variation is when the individuals in a population vary within a range, e.g. low amount for minimum a lot for average and low amount for maximum. Examples of discontinuous variation could be height, weight and skin colour. Continuous variation is usually shown on histograms.
What is discontinuous variation?
Discontinuous variation is when the categories are very distinct and not in an order. Examples of discontinuous variation could be blood groups, eye colour, and biological sex. Discontinuous data is usually shown in bar charts.
What is heterozygous?
Heterozygous is used to describe a person with two different alleles, e.g. Bb.
What is homozygous?
Homozygous is used to describe people with two of the same alleles, e.g. BB or bb.
What is a mutation?
A mutation is a change in the DNA code so a protein that genes code for might be different. Most mutations have have an affect on proteins therefore don’t change the organisms phenotype at all. However if mutations affect proteins the phenotype will slightly change (usually bad and unwanted, very occasionally good)
What is an example of a mutation?
An example of mutations are resistance to lung disease
What determines the sex of a male?
In males, the 23rd pair of chromosomes contains an X and a Y chromosome.
What determines the sex of a female?
In females, the 23rd pair of chromosomes contains two X chromosomes.
