genetics and evolution Flashcards
What is a gamete
a male or female sex cell that can fertilize during sex to form a zygote
what is a zygote
a single cell formed by the fusion of 2 gametes
what does DNA stand for
deoxyriboncleic acid
what is a gene
section of DNA which codes for specific charcteristics
Chromosomes
A length of DNA made up from genes. Humans have 46 genes
what does ATGC stand for
A=adenine
T=thymine
G=guanine
C=cytosine
what is a mutation
an accidnetal alteration in agenetic message. Could be harmful or helpful.
what are there causes of mutations
- radiation
- damage during cell divison
- chemicals, drugs, smoking
what is a genotype
genes responsible for charcateristics of an indivdual e.g. hair, eye colour
what is a phenotype
the physical charcteristics e.g. brown hair blue eyes
what is a dominat gene
an allele which shows its effect when there is only one allele of a pair e.e. hitchhikers thumb, right or left handed
what is a recessive gene
A gene that is not expressed if the dominant allele is also present
what is cell divison
Meiosis and mitosis
what is meiosis
cell divison responsible for producing sperm or egg cells 4 daughter cells
what is mitosis
cell divison responsible for growth and repair 2 daughter cells
what is varaiton
the diffecrence between individuals caused by the combination of genes and the enviroment we live in
what is discrete varation
Characteristics controlled by a single gene tend to have phenotypes that fall into separate categories
what is continous varation
a characteristic that changes gradually over a range of values
what is selective breeding
choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics.
what are the 4 theories of evolution
- Bone
- Chemical
- Embryo
- Fossil
