3.2.3 Genetic Inheritance Flashcards
What is a gene
A gene is a short length of DNA found on a chromosome that codes for a particular characteristic
What are Alleles
Alleles are variations of the same gene
- As we have two copies of each chromosome, we have two copies of each gene and therefore two alleles for each gene
- One of the alleles is inherited from the mother and the other from the father
- This means that the alleles do not have to ‘say’ the same thing
- For example, an individual has two copies of the gene for eye colour but one allele could code for brown eyes and one allele could code for blue eyes
The observable characteristics of an organism is called, what?
the phenotype
The combination of alleles that control each characteristic is called, what?
the genotype
Alleles can be dominant, or?
or recessive
A dominant allele only needs to be inherited from one parent in order for, what?
the characteristic to show up in the phenotype
A recessive allele needs to be inherited from both parents in order for, what?
the characteristic to show up in the phenotype
If there is only one recessive allele, what happens?
it will remain hidden and the dominant characteristic will show
If the two alleles of a gene are the same, we describe the individual as being, what?
homozygous (homo = same)
Define homozygous dominant
having two copies of the dominant allele
Define homozygous recessive
having two copies of the recessive allele
An individual could be both, homozygous ____, or homozygous ___
homozygous dominant or homozygous recessive
We describe the individual as being heterozygous if, what?
If the two alleles of a gene are different
When completing genetic diagrams, alleles are abbreviated, to what?
to single letters
Which allele is given a capital, or lower case
The dominant allele is given a capital letter
the recessive allele is given the same letter, but lower case
We cannot always tell the genotype of an individual for a particular characteristic just by looking at the phenotype – a phenotype associated with a dominant allele will be seen in both, what?
a dominant homozygous and a dominant heterozygous genotype
If two individuals who are both identically homozygous for a particular characteristic are bred together, what happens?
they will produce offspring with exactly the same genotype and phenotype as the parents
- we describe them as being ‘pure breeding’ as they will always produce offspring with the same characteristics
A heterozygous individual can pass on different alleles for the same characteristic each time it is bred with any other individual and can therefore, what?
produce offspring with a different genotype and phenotype than the parents – as such, heterozygous individuals are not pure breeding
Gamete Definition
Gametes are sex cells
Chromosomes Definition
Chromosomes are threat-like structures of DNA, carrying genetic information in the form of genes. They are located in the nucleus of the cell.
Gene Definintion
Genes are short lengths of DNA found on chromosomes. They code for specific proteins
Allele Definiton
Alleles are different versions of a particular gene.
Dominant Definition
A dominant allele is always expressed, even if only one copy is present.
Recessive Definition
A recessive allele is only expressed if two copies are present
