Key Area 4 - Inheritance Flashcards
What is a gene?
Part of a chromosome controlling one characteristic
What are alleles?
Different forms of a gene that control a characteristic
What does dominant mean (in terms of genes)?
Allele that always shows itself in the phenotype
What does recessive mean ( in terms of genes)?
Allele that is masked by a dominant one
What does genotype mean?
The genetic makeup (complete set of genes possessed) of an organism (always written in letters e,g TT)
What does phenotype mean?
The outward (physical) appearance of an organism (always written in words)
What does diploid (2n) mean?
Having two sets of chromosomes in the cells - normal cells
What does haploid (n) mean?
Having one set of chromosomes in the cells - sex cells/gametes
What does True Breeding mean?
An organism that has either 2 dominant (e.g TT) or 2 recessive alleles (e.g tt)
What does homozygous mean?
A condition in which an organism has two identical alleles of a gene e.g TT or tt
What does heterozygous mean?
A condition in which an organism has two different alleles of a gene e.g Tt
What is continuous variation?
Can be measured, large range of values (polygenic, determined by more than one gene)
e.g. Height, Mass, Foot Length
What is discrete variation?
Can be put into categories (single-gene inheritance)
e.g. Gender, Blood group, Eye Colour
What is variation?
Differences between individuals of the same species that aren’t caused by accident or disease
Why is it that children resemble but aren’t identical to their parents?
- Each parent has two different sets of genes
- Each parents passes only half of their gene
- The half that gets passed down is random
What are used to symbolise genes and alleles?
Letters
With allele is given the capital letter?
The dominant allele
Therefore, which allele is given the lower-case letter?
Recessive allele
What can be used to help us work out the genotypes?
A Punnet square
What are homozygous individuals also referred to?
True-breeding
Why is there often a difference between the observed and the predicted numbers of different types of offspring?
As fertilisation is a random process.
What does polygenic mean?
Determined by more than one gene, they show continuous variation
How many alleles does every body cell have?
Two alleles
What is the dominant phenotype?
The phenotype that appears most often
