Variation + DNA (paper 2) Flashcards
Differences in the characteristics of individuals in a population is called
variation and may be due to differences in:
- the genes they have inherited (genetic causes)
- the conditions in which they have developed (environmental causes)
- a combination of genes and the environment.
usually what is the range of variation within a species
there is usually extensive genetic variation within a population of a species
what do all variants arise from
mutations
do mutation have an effect on its phenotype
most have No effect and some *influence** phenotypes , very few determine phenotype
what is the phenotype
the physical characteristic of an organism which occurs as a result of its genes
What are mutations, and how often do they occur?
Mutations occur continuously
How and how often can a mutation lead to the evolution of a species in response to environmental changes?
-
Very rarely a mutation will lead to a new
phenotype - If the new phenotype is suited to an environmental change it
can lead to a relatively rapid change in the species
species definition
individuals that share many characteristics and can reproduce to make fertile offspring
describe the 4 key characteristics of a genetic source of variation
- some characteristic are inherited from our parents
- these characteristics are determined by our inherited genes
- our genes control the development of our characteristics
- each characteristic is controlled by a single gene
what is the cause of environmental cause of variation
some characteristics can be altered and changed by lifestyle choices
what is continuous variation
these characteristics show a range of many intermediates between 2 extremes
what is discontinuous variation
different characteristics with no intermediates between them
how is continuous data often represented
histogram with a range of characteristics divided into different classes
how is discontinuous data often represented
bar chart
what does DNA stand for
Deoxyribonucleic acid
what is genetic material in the nucleus of a cell composed of
a chemical called DNA
describe the structure of DNA
- is a polymer - large molecule made up of repeating subunits = nucleotides
- made of 2 strands which spiral round = double helix
what does DNA contain
chromosomes
gene definition
- A gene is a small section of DNA on a chromosome that codes for a specific sequence of amino acids to make a specific protein
- this protein determines a characteristic or trait
what does a gene do
Each gene codes for a particular sequence of amino acids, to make a specific protein
what is the genome of an organism
entire genetic material of that
organism.
why will genomes be of great importance in the future
whole human genome has now been studied and this will
have great importance for medicine in the future.
how many nucleotide make up DNA
4 different nucleotides
what does each nucleotide consists of
a common sugar and phosphate group with one of 4 different basses attached to the sugar
what are the 4 bases found in DNA
A, T, C, G
what do the long polynucleotide stands of DNA consist of
- alternating sugar and phosphate sections
- attached to each sugar is one of the 4 bases
what happens in complementary base pairing
complementary strdans of the double helix:
- C is always linked to a G on the opposite strand
- T to A
what codes for a particular amino acid
a sequence of 3 consecutive bases
what is the effect the order of the bases have on an amino acid
order of bases controls the order in which amino acids are assembled to produce a particular protein.
what is a locus
the position of a gene on a particular chromosome
allele definition
an alternative form of a gene that codes for the different variation of a specific trait
describe the process of protein synthesis
Stage 1 (in nucleus): Transcription:
1. base sequence of the gene is copied into a complementary template molecule called mRNA
2. mRNA is a single-stranded molecule
3. mRNA passes out of nucleus (is smaller than DNA, able to pass out of nucleus) into the cytoplasm
Translation:
4. mRNA molecule attaches to a ribosome
5. amino acids brought to ribosome on carrier molecules / tRNA
5. ribosome reads triplets of bases on the mRNA and chemically join together the correct amino acids in the correct order
6. one protein chain is complete it now folds up to form a unique shape
8. the unique chape enables the protein to carry out its specific function
what are functions a protein cab do
- **enzymes
- hormones
- forming structures in the body such as *collagen**
how often do mutations occur in the DNA
continuously
what are mutations
alterations to the base sequence in the DNA
what is the effect mutations have on a protein
- most do not alter the protein
- or only alter it slightly but appearance or function is unchanged
what are the 4 types of point mutations
- substitution : ATG —> ACG
- insertion: ATG –> ATCG
- deletion: ATG –> AG
- inversion: ATG –> AGT
what effect coulf a mutation have on a protein
- change in base = different amino acid = change shape of protein
- dramatic effect:
- active site of an enzyme may change shape (no longer complementary –> can no longer attach to the substrate
- if mutation changes shape of structural protein (collagen) then it may lose its strength
non coding DNA =
DNA that does not code for a protein, instead turns genes on and off
where contains non-coding DNA
chromosomes
what are non-coding DNA sometimes called
introns
what are sections of DNA that code for protein called
exons
of mutations occur in non-coding section of DNA this can:
- prevent some genes being switched on = protein not made
- prevent some genes being switched off = protein made continuously
- variations in these areas of DNA
may affect how genes are expressed
