Variation and Inheritance Flashcards
What does the DNA molecule consist of
Two strands, coiled to form a double helix
What is the chemical code in DNA made up of
Four bases which hold the two strands of the molecule together
How many matching pairs of chromosomes do human have in cells
23 pairs
46 in total
What cells in the body have 23 individual chromosomes
The gametes
Fuse to produce zygote with full number of chromosomes
This process increases variation in a species, genetic information from parents mixes to create new unique individual
What happens regarding genes in asexual reproduction
All genes come from one parent
Offspring are genetically identical, clones
Genetic variation between individuals can be caused by
Mutations which alter the genes
Genes and chromosomes shuffled gametes
Random fusion of egg with one out of millions of sperm at fertilisation
What are the genes which code for characteristics called
Alleles (occur in pairs)
These are alternative forms of a gene
In sex chromosomes what determines a male and female using X and Y
Female XX
Male XY
What is a dominant allele
Inherited characteristic even if it is present on only one chromosome in a pair
What is a recessive allele
Both pairs of chromosomes have to have recessive allele for it to be inherited
What is it called if chromosomes in a pair contain different alleles of a gene
The individual is heterozygous for that gene or condition
What is the genotype
A characteristic you can’t necessarily see (in the mirror)
What is the phenotype
A characteristic you can see (in the mirror)
What is it called when a characteristic is determined by just one pair of alleles
Monohybrid inheritance
What are some inherited diseases
Red-green colour blindness:cells in eye cannot distinguish btween red and green light
Sickle cell anaemia: red blood cells become misshaped leading to circulatory problems and oxygen deficiency
Cystic fibrosis: cell membranes produce excess mucus that blocks airways and causes problems with digestion
