Science - Genetics and Evolution Flashcards
What is a zygote
A single cell formed by the result of the fusion of two gametes
Where is the embryo attached
The uterus but does not resemble the shape of a baby
What are haploid cells
One set of chromosomes
One chromosome in a human = 23
In humans, gametes are haploid
What are diploid cells
two sets of chromosomes
Two chromosomes in humans = 46
In humans, all body cells other than gametes are diploid
What is DNA
The instruction of physical characteristics
What are DNA’s four base pairs
G, C, T, A
What is DNA found in
the shape of the double helix or a twisted staircase helix
What are genes
A section of DNA for a specific characteristic eg hair colour and height
What are chromosomes
a length of DNA which is made up of many genes. Chromosomes are stored in the nucleus of a cell
What is an allele
a different form of a gene eg if a gene is hair, the alleles is black, brown, blonde, or red
What is dominant
in geneitcs, an allele which shows its effect when there is only one allele of a pair. it is represented by uppercase letters
What is recessive
A gene that is not expressed if the dominant allele is also present
What is homozygous
A genotype is homozygous when it is made up of two of the same allele
What does homo mean
the same
What is heterozygous
A genotype is heterozygous when it is made up of two different alleles
What is discrete
Characteristics where you are either one thing or another which are inherited and usually controlled by one pair of genes
eg you are male or female
What is continuous
Where most genetic differences are not either/or. These features are usually controlled by one or more pairs of genes.
eg skin colour, weight
What is mitosis
Cell division responsible for growth and repair
What is meiosis
cell division responsible for producing sperm or egg cells
What is selective breeding
Choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics
eg humans selectivity breed farm animals with better quality meat or wool
What is fitness
The context of natural selection is the measure of success. If an individual is ‘fit’ it is more likely to find a mate and reproduce
What is natural selection
A species ability to adapt to a changing environment
What is evolution
the change in characteristics of a species over several generations and relies on the process of natural selection
What is a scientific theory
a well-tested, broad explanation of a natural phenomenon
