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
What is canatomical evidence
Where most mammals have the same 1-2-5 arrangement of arm and leg bones
What is chemical evidence
similarities between biological molecules that reflect shared evolutionary ancestry
All living organisms share
- DNA
- The same of highly similar genetic codes
- the same basic process of expressing genes with physical characteristics
- the same molecular building blocks such as amino acids
What is fossil evidence
documenting the evidence of now-extinct species showing that different organisms have lived on Earth during different periods of the Earths history
What is a punnet square
a table which all outcomes between 2 individuals with known genotypes are given
What does genotype mean
Genotype: refers to the exact pairing of alleles eg B = blue b = green there are 3 possible outcomes
BB, Bb, bb
What does phenotype mean
Phenotype: the expression of the trait and where two alleles work together to create what people can see eg B = blue b = green there are 2 possible outcomes as genotypes
BB and Bb both give the same phenotype which is blue
What is a cell
the smallest unit that can live on its own and that makes up all living organisms and the tissues of the body
What are characteristics
a distinguishing quality, trait, or feature of an individual, thing, disorder, etc
What is a mutation
an accidental alteration in a genetic material which can be big or small, harmful or helpful
What is variation
The differences in characteristics within a population which can be caused by mutations (environment or genetics)
3 examples of mutations
Cystic fibrosis
Cancer
Lactose intolerance
What is a gamete
a reproductive cell of an animal or plant
