variation, genetics & inheritance (paper 2) TOPIC 6 Flashcards
variation definition
differences in the characteristics of individuals in a population
what do all variants arise from
mutations
define genetic variation
characters determined by the genes we inherit from parents
give some examples of genetic variations
- eye colour
- blood group
what do our genes control
the development of our characteristics
define environmental variation
charcateristics that can be altered or changed by lifestyle
give some examples of some environmental variation
- tattoos
- scars
what ar ethe two different categories of variation that can be represented on a graph
- continuous
- discontinuos
define mutation
a change in the DNA base sequence
what is the effect of a CGT nucleotide rather than CTT
a different amino acid is coded
if a protein is mutated and it is an enzyme, why might this mutation stop it from functioned
it can lead to a different shaped active site, which is complimentry
what is the name of A
base
what is the name of B
sugar
what is the name of C
phosphate
what are the names of the 4 different types of bases
- C
- T
- A
- G
which bases pair with which in a DNA structure
- C pairs with G
- A pairs with T
what is the name given to the structure of DNA
double helix
what is the name of this whole diagram
nucleotide
define a gene
a sequence of DNA that codes for a specific sequence of amino acids
define an allele
different forms (varients) of a single gene
define genotype
the combination of allelels of a single gene
define phenotype
an organisms appearance or characteristic
define homozygous
having two identical alleles for a particular gene (BB or bb)
define heterozygous
having two different alleles for a particular gene (Bb or bB)
in which organelle are proteins made
ribosomes
how many bases code for one amino acid
3
what is embryo screening
when the embryo is tested during the course of pregnancy to detect inherited diseases
name a condition embryos may be screened for
cystic fibrosis
what are some of the ethical issue with embryo screening
- can result in abortions
- miscarridge risk increases
- embryo’s cannot give consent
- parents may choose genetic makeup of child
is DNA an example of a polermer yes or no
yes
what does DNA stand for
deoxyribonucleic acid
what is the genetic material inside a nucleus called
DNA
what are chromosomes
the structures the DNA is contained
what is a genome
the entire genetic material of an organism
how many chormosomes in a human nucleus
46 chromosomes
explain what is meant by ‘the gene is expressed’
when a gene codes for a protein that is synthsised in the cell
describe the steps of protein synthesis
- the DNA molecule is too big to leave the nucleus
- a template is made
- the template leaves via a nuclear pore because it is small enough
- template goes out to a ribosome in the cytoplasm
- carrier molecules attach to the template in order
- when chain is complete, detaches from ribosome and folds to a specific shape
what are proteins synthesised on
ribosomes
what is the template determined by
the sequence of bases in the DNA molecule
what do carrier molecules do in protein synthesis
bring specific amino acids to the chain
why does the protein chain fold into a unique shape
it enables it to carry out its function
define mutation
a change in the base sequence of a section of DNA coding for a specific trait
what is the effect of a mutation
- it may change the amino acid sequence of a protein
- this changes its shape of the active site
- and it may be non functional
what does non-coding DNA do
switch genes on and off
what does coding DNA do
code for specific proteins
which allele is always expressed: dominant or recessive
dominant
when is a dominate allele expressed
all the time even when only one copy is present
when is a recessive allele expressed
when 2 copies of the allele is present
what do you use to determine allele combinations for an offspring for one gene only
a punnett grid
does a punnett grid determine alleles for all the genes
no only one
what are the two inherited disorders we study
- polydactyly
- cyctic fibrosis
what is polydactyly
having extra toes or finger
what type of allele is polydactyly caused by
a dominant allele
what is cystic fibrosis
a disorder of cell membranes
what type of allele is cystis fibrosis caused by
two recessive alleles
what are people called that have one recessive allele of a disease
a carrier
what procedure can be carried to see if an offspring will have an inherited disorder like cystic fibrosis
embryo screening
what are the female sex chromosomes
XX (the same)
what are the male sex chromosomes
XY (different)
what are the two methods for embryo screening (do not need to know fully just in case of reference)
- aminocentisis = fluid from around feotus
- chorionic villus spampling = sample of tissue from placenta
what are the advantages of embryo screening
- doctors can determine if the child will have an illness or disease
- it prepares parents
- allows parents to decide to have children or not
what are the disadvantage of embryo screening
- can result in unborn child being aborted
- can cause miscarridge
- expensive
- goes against religious beliefs
