lecture 2 - variation Flashcards
when we look at trends in variations in populations what is found?
bell shaped curve - many ppl have an average, some are tall and some are small - could be due to environment or genetics
what is a genotype?
genetic makeup – kinds of genes that you have
what is a phenotype?
expressed traits, things we can measure e.g. height
made up of genotype and environment
what is DNA made up of?
2 sugar phosphate backbone (spb)
what does DNA do?
Attached to each spb – organise in pairs – bases attract each other, in between is a hydrogen bond, allows the molecule to unzip,
Always pair up in a similar way
what are the 4 bases?
guanine and cytosim
adenine and thymine
these can code for 20 diff amino acids used in various proteins
what is a gene?
section of the chromosome that codes for a particular protein
how do we determine the function and structure of something?
the codes for the bases in the format that amino acids are put together
do we all have the same genes?
yes, we just have diff versions of them - diff variants/alleles e.g. green or blue eyes
what is transcription?
Start with the DNA molecules – splits down the middle via hydrogen bonds breaking, alongside RNA will form – same as DNA except it has the base uracil – copying process
what is translation?
Molecule of RNA – travels out of the nucleus into the cytoplasm, ribosomes form around and reads the code, putting together the amino acids in the way they should and makes the protein
what is a stop codon?
tell the ribosome to stop as the protein is complete – can see how many genes there are
who discovered the genome?
Crick and Watson
Rosalind Franklin was involved but died before the Nobel Prize was given
what is non-coding DNA?
-May be parasitic
-Includes many transposable elements
-Includes many simple sequence repeats
-Some is highly conserved
-Some may serve regulatory functions
what is the most common example of a retrovirus?
HIV - injected and can be copied
what is a transposable element?
chunks of DNA that are good at getting copied
what are simple sequence repeats?
get extra copies added than the original has in cell reproduction
when comparing genomes what was an interesting trend found?
the num of genes an organism has doens’t differ that much
- more complex organisms have bigger genomes than more simple
can siblings have diff subsets of genes from mum and dad?
yes
how are diploid organisms or cells arranged?
in pairs
what is mitosis?
cell reproduction - each chromosome splits down the middle so that there are 2 of everything, the bases line up and split again – daughter cells have 46 chromosomes each – 2 cells left which are identical
what is meiosis?
one of every kind of chromosome rather than 2
23 chromosomes from dad and 23 from mum – out of these need 1 of each chromosome (1,2,3etc) and only one of each pair gets copied and goes forward into the gametes – this is done at chance so about half come from dad and half from mum
what is crossing over?
Chromosomes pair up during the copying process – each decision as to which will be copied will be at random
what is a single base substitution? (mutation)
when one base is put in the wrong place
what is a simple sequence repeats? (mutation)
get an extra one copied in during mitosis or one fewer than is actually there
what is a segmental change? (mutation)
when you get an entire additional chromosome – downsyndrome, extra sex chromosome – XXY, XYY
what does it mean if a mutation has no phenotypic effect?
theyre neutral - change in one of the base pairs within a gene but will still code for the same amino acid , redundancy in bio systems – often numerous ways to do stuff in the body so if a mutation is caused it will be taken over by a diff way of doing things
what does it mean if a mutation has deleterious effects?
theyre harmful - more ways to get things wrong than make them better – things are so finely tunes, if do it diff most likely will be worse
e.g. cystic fibrosis, haemophilia, Huntington’s disease
How do you find the genetic basis of a phenotypic characteristic?
Collect data from large fams where some individuals have traits or diseases and use them as particular markers on the genomes – to see which are shared with sufferers and non sufferers – can work out what part of the chromosome causes the effect we are seeing
More achievable as we have become better at genetics – many genetic markers at the same time – large group of individuals as long as some have the trait and others don’t – can look at the alleles and see which play some roles in it
