Genes and Proteins Flashcards
Where are chromosomes present?
In every cell of the human body - every living organism has a unique genetic make up
What cells don’t have 2 copies of every chromosome?
Gonads
Where is the information carried?
In our DNA
What is DNA?
Long-strands of ladder like structure
Double helix structure made from 2 chains
Discovered in 1050’s
What is the DNA wrapped around?
Proteins, which is condensed into chromosomes in the nucleus of the cell
What are the 2 chains of DNA made from?
Phosphate and deoxyribose (type of sugar)
What does DNA consist of?
4 nucleotide bases adenine thymine cytosine guanine
go in pairs: a&t and c&g
ladder formed of compliments of these
What does the genetic code consist of?
Chain of letters of all the nucleotide pairs together - it is that code which you unravel, and can read proteins from it - make cells determine what they will look like
What is the purpose of DNA?
To make the organism individual
some is coding but some is regulatory
How many genes are on human chromosomes?
Approx 23,000 genes
What are genes?
Long sequences of base pairs in the DNA which encode proteins
How are genes turned on?
Transcription factors
What are transcription factors?
Proteins which convert DNA to RNA - in the nucleus, the genes DNA is copied into messenger RNA
transcription factor turns on a gene, making a protein
When are transcription factors activated?
During development or by intracellular signalling cascades from other parts of the cell
different cells have characteristics expressed by different transcription factors - switch on the genes which are needed
How does the transcription factor bind to a gene? How does genes to protein happen?
The DNA partially unravels - transcription factor goes along and copies DNA sequence to make single stranded RNA. Makes proteins out of a chain of amino acids
How many amino acids are there?
Only 20 but can make loads of proteins from the different genes
What is translation?
A ribosome attaches to the mRNA and moves along the mRNA, reading each triplet codon (3 bases) and using transfer RNA’s to put together the amino acid chain to make a protein
What is mitosis and meiosis examples of?
A form of cell division
What is mitosis?
Somatic cells (cells in our bodies) replicate to make identical copies of the DNA. the cells divide into 2 and just keep dividing and dividing into identical copies
What is meiosis?
Gametes - dividing to make the DNA content which is passed onto the next generations
when the chromosomes duplicate, the cells segregate and divide, so instead of being identical, have bits from maternal and paternal chromosomes
this is what makes you different from your mum and dad
What are the haploids?
These are the gamete cells - sperm or egg
What does crossing over mean in meiosis?
Homologeous recombination -nucleotide sequences are exchanged between two similar or identical molecules of DNA - allows genetic diversity, by mixing up what the chromosomes look like
Why is homologous recombination important?
Allows for natural selection - need diversity, so if something happens in the environment, some people will be more favourable to it than others
Why is our DNA different to our siblings?
We share 50% of parents genes but a different 50% - due to meiosis
What is mendel’s law?
States that during the formation of reproductive cells (gametes), pairs of hereditary factors (genes) for a specific trait separate so that offspring receive one factor from each parent
What are the two forms of genes?
Dominant and recessive
What did mendel discover?
Inherited properties in pea plants - tall vs dwarf. there is a trait that is controlled by a single gene
What is it called when genes are identical?
Homozygous - TT or dd
What is called when genes aren’t identical?
Heterozygous - Td
What are dominant vs recessive genes?
dominant allele - produces a dominant phenotype in individuals who have one copy of the allele, which can come from just one parent.
recessive allele to produce a recessive phenotype, the individual must have two copies, one from each parent.
an individual with one dominant and one recessive allele for a gene will have the dominant phenotype. They are generally considered “carriers” of the recessive allele: the recessive allele is there, but the recessive phenotype is not
What is an allele?
Different forms of the same gene
specifies what form the gene takes
How many alleles do each individual have?
2 for each trait
What is a genotype?
The possible pairings of the alleles so either: BB bb Bb only concerned with the pairings
What is phenotype?
The expression of the trait
e.g. blue eyes
What is a gene?
Specifies for the trait
Sections of DNA
How are the 2 strands of DNA helix held together?
By the nucleotide base pairs
Where are chromosomes held?
In the nucleus of each cell
