Chromosomes, Genes and Proteins Flashcards
What is a chromosome?
A structure containing DNA, found in a cell nucleus.
What is DNA?
A molecule containing genetic information in the form of protein sequences
What is a gene?
A strand of DNA that codes for the production of one protein
What is an allele?
A variation of a gene. i.e.
gene = eye colour
allele = brown
What is the structure of a chromosome like?
Two identical chromatids with a centromere joining the two together
How are chromosome pairs identified?
By size and shape.
Side Note: In a nucleus the chromosomes are floating around and not attached to their pair.
Outline the process of mitosis with a cell containing 46 chromosomes.
Parent cell has 46 chromosomes
2 Daughter cells are formed with 46 chromatids.
Exact copies of the chromatids are made to result in 46 chromosomes in each daughter cell
Outline the process of meiosis with a cell containing 12 chromosomes.
(You don’t really need to know all of this, but it is good to understand)
Parent cell contains 12 chromosomes.
Homologous chromosomes pair up and then separate into 2 daughter cells.
(6 pairs are formed)
Each daughter cell now has 6 chromosomes. These divide with mitosis to form 4 cells with 6 chromatids. These grow to create 4 daughter cells with 6 chromosomes
Which type of cell division produces diploid daughter cells?
Mitosis
Which type of cell division produces haploid daughter cells?
Meiosis
What is the difference between a homozygous and heterozygous gene
Homozygous = two identical alleles i.e. BB or bb
Heterozygous = two different alleles i.e. Bb
What is the difference between genotypes and phenotypes?
Genotype = genetic makeup of an organism in terms of alleles present
Phenotype = the observable features based on the dominant allele only.
How are dominant and recessive alleles expressed
Dominant - Capital Letter
Recessive - Lowercase Letter
What is codominance?
When 2 different alleles are expressed in a phenotype.
How is the genotype of an offspring determined, in terms of gametes?
(Using an example of two heterozygous parents with alleles G dominant and g recessive)
The male produces an equal amount of G and g sperm. The female produces one egg of type G or g (50/50 chance).
Possible outcomes:
25% - GG (dominant homozygous)
50% - Gg (dominant heterozygous)
25% - gg (recessive homozygous)
