6- Inheritance, Variation And Evolution Flashcards
Sexual reproduction
- involves the joining of male and female gametes formed by meisosis
- mixing of gentic material taes place- variation
- takes more time and energy, need a mate and 2 parent cells
Meiosis
- produces games
- parent cell- diploid- full set of chromosomes in pairs
- DNA replicated
- two sets of cell division
- produces 4 genetically different gametes each with a single set of chromosomes-haploid)
Haploid
Only has half the number of chromosomes
One set
Fertilisation
- one gamete cell each sex - egg and sperm
- fertilisation
- produces diploid zygones
- mitosis
- diploid embryo
Genome
The entire genetic material for an organsim
Human genome project
Sequencing the entire human genome
Uses of the human genome project
- targeted medicines/treatments
- identifying/understanding cause for genetic risk factors for disease
- evolutionary relationships/migration patterns
- identifying genes
Alleles
Different form of gene
2 alleles per gene
(1 from each parent)
Dominant
Always expressed in phenotupe if present
Capital letters
Reccessive
Only expressed in phenotype if both are present
Lower case
Homozgous
Two. Alleles are identical
BB or bb
Heterozygous
Two aleles whch are diff
Bb
How to find out probability certainproperty is had
- write out phenotype
- write out gametes
- draw punnet squares and times out
- find out percentage
Sex determination
- 1 chromsome determines this
- female XX
- males XY
- use normal genetic cross
Genotypic ratio
Dominant : recessive
Phenotypic ratio
Ratio of visable trait
Structure of DNA - when discovered
- 1953
- james watson and francis crick at cambridge
- rosalin franklin- xrayed it
Where is genetic material found
Nucleus
DNA
DNA
A polymer made up of two strands forming a double helix and nucleotide monomers
Contained in structures called chromosomes
Gene
A small section of DNA in a chromosome
- each gene codes for a partiicular sequence of amino acid \
- to make a protein
Nucleotide made up of
- base(in middle) bound with hydrogen double bond
- glucose/sugar
- two phosphate molecules
Structure of dna
-double helix
-sugar phosphate backbone
-hydrogen bond between bases
-made up of 4 complementary base pairing
A+T. G+C
Mutations
A spontanous/random change to the sequence of nucleotides
How mutations affect protein- coding region
- a change in base may result in a change in AA
- change in AA sequence may lead to protein that has a diff structure and so changes function
- eg. Shape of enzyme active site may mean not complimentary to substrate
- or could improve the sturcture eg. Its strength
Mutation - non-coding region
-mutation may switch a gene on or off making protein when needed or not
Point mutation
- 1 base change
- change to 1 codon
Insertioon/deletion
Changes every codon after mutation
Polydactyly
- having extra finger or toe
- caused by dominant allele
- only need 1 parent to get it
Cystic fibrosis
- disorder of cell membrane
- caused by lack of regulation of water and ions in an out of certain cells inc tissue in lung
- sufferes produce mucus that’s thicker than normal making it more diff to breath
- cough a lot
- diff putting on weight
- affects digestive system
- tiredness- aneamia
- easier to catch infections
- recessive allele
Asexual reproduction
- mitosis takes place
- 1 parent cell needed- no genetic mixing of info
- genetically identical offspring
- v. Quick so many offspring can take advantage of favourable conditions
- no need to find a mate
- less energy
- when all cells genetically identical, disease affects the whole population
Examples of organisms that ue both asezual and sexual reproduction
- malaria
- fungus spore
- strawberry plants
- bulb plants eg. Daffodil
Malaria
- parasite reproduces sexually in mosquito
- asexually in human/animal
Fungus spores
-sexually produced spores introduce variation and often produced in response to unfavourable change in environment, so spore more likely to survive change
Strawberry plants
Produce runners with identical strawberry plants on them
Bulb plants (daffodils)
New bulbs can form from main bulb and divide of, each new bulb can grow into a new identical plant
Codon
- 3 nucleotides/bases in a sequence
- have 23 codons
- 20 AA
- 3 stop coding codons
- each codon codes for one specific AA by binding to a complementary tRNA molecule into AA attatched
- order of bases controls order in which amino acids are assembles to produce particular protein
Transcription
- DNA sequence copied in a molecule of mRNA
- in nucleus
- opposite base in mRNA
- have no T so has U instead
Translation
- nucleic acd to AA/poly peptide
- mRNA carries a copy of gene to a ribosome (exits nucleus to cytoplasm)
- ribosome takes in mRNA
- carrier/tRNA attatched to AA
- tRNA move to ribosome and attatches mRNA for particular use
- two AA next to each other bod-strong polypeptide change
- amino acids released into cytoplasm
- continues until reaces into cytoplasm
- continues until reaches stop codon in which polypeptide is released into cytoplam
- in cytoplasm, polypeptide folds into protein shape
