B6 Genetics Flashcards
Describe structure of DNA
DNA has a double helix structure
Made up of two strands
DNA strands are complementary
DNA strands are held together by complementary bases
DNA has four bases - C,G,A,T
C pairs with G, A pairs with T
The sequence or code of DNA determines what characteristics we have
A long sequence of DNA is called a gene
DNA is packaged as chromosomes in the nucleus
Gene
Small sections of DNA that code for a protein. Different amino acids can code for different proteins
Genome
The entire set of genetic material in an organism. This can be used to see if a certain group of people are more susceptible to a disease.
Chromosone
A section of DNA that are tightly coiled. There are 46 in total so 23 pairs. And 23 in a gamete
Alelles
Alleles are different versions of the same gene
Full explanation
Transcription
Transcription- The first step of protein synthesis. Taking a single gene of DNA and copying into a structure called mRNA.
Gene to be copied is sectioned
Then enzyme RNA polymerase starts just infornt of the gene that is to be copied moves along the gene.
The 2 strands of the DNA split so that the enzyme can bind to the bases. mRNA bases always compliment DNA.
The enzyme moves along copying the template strand that creates mRNA.
The DNA strand then closes up.
What makes mRNA different to DNA
mRNA is much shorter than DNA
Only a single strand
Contains Uracil
Why must translation and transcription occur
As ribosomes are located outside the nucleus. The DNA is too long to be transported outside of the nucleus. So a smaller copy must be produced thats small enough to leave the nucleus.
Translation
Translation- This is the process where mRNa is converted into protein.
The mRNA is carried by tRNA molecules that carry it to the ribosome. The ribosome binds to the mRNA strand.
At the bottom of each tRNA molecule there is an anticodon that is complimentary to the mRNA molecule. The ribosome moves along the chain of mRNA. Producing an amino acid. As the ribosome moves along the chain. The tRNA molecules arrrive and as the amino acid upon them is produced and the ribosome moves along allowing for the amino acid to form a chain and the tRNA to move elsewhere. Forming a chain of amino acids that folds in on itself to make a protein
Mutations and what increases their risk
A change in the DNA’s base sequence and can be increased by carcinogens and certain types of radiations
Definition
Meiosis
Mitosis
Meiosis produces 4 daughter cells which are all genetically different to the parents
Mitosis produces 2 daughter cells which are identical to the parent
Types of mutation
Insertion-When a new base is inserted into a space it shouldn’t be. They change the way the codons are read
Deletion-When a random base is deleted from the base. They change the way that the base is read.
Substitution-When a random base is changed to a different base
Sexual reproduction 3 pros/cons
Sexual Pros
Variation increases chance of survival
These individuals will be better suited to the enviroment so are to breed succesfully and pass these charchteristics on
Selective breeding can speed up natural selection which can increase food production
Sexual Cons
More energy is needed to find a mate
Slower
Homozygous
Heterozygous
Homozygous-2 allelles that are the same
Heterozygous-2 different alleles that are different
Phenotype
Genotype
Genotype- Combination of alleles you have
Phenotype-The physical charactericstic you present
Explain 2 inherited disorders
Cystic Fibrosis- A reccesive allele which causes sticky mucus to build up in the kungs
Polydactyl- A dominant allele which allows for extra fingers or toes
Pros/Cons embryo screening
Pros
Help kids stop suffering
Costs goverment a lot
Already laws to stop it going too far so cant select sex of baby
Cons
Implies people with genetic issues could increase prejudice
Expensive
A point in time where everyone screens their embryo to pick the ‘best child’
Meiosis
Duplicates gentetic information forming 2 armed chromosones X and they are a exact copy of each other
Chromosone pairs line up the centre of the cell
Pairs are then pulled apart so each new cell has one copy of chromosne
In second division chromosnes line up again and are pulled apart
You get 4 gametes with a single set of chromsones. Each of the gametes is genetically different
2 reasons why Mendels discoveries werent believed
Mendel was not part of an academic establishment
Scientists did not know about chromosones
3 conclusions from Mendel
Characterisitcs are determined by heriditary units
Units are passed on to offspring unchaged 1 unit from each parent
These can either be dominant or recessive- if an individual has both dominant it will be presented
