Genetics - topic 3 (pg 20-28) paper 1 Flashcards
meiosis
produces four daughter cells each with half the number of chromosomes
only in gamete producing cells, producing genetically different haploid gametes
haploid
one set of chromosomes (me-1-osis)
stages of meiosis
the parent cell is a diplod cell (two pairs of chromosomes –> parent cell dividesin two then two again
- before the parent cell divides, each chromosome is copied
- each daughter cell gets a copy of one chromosome form each pair
- each daughter cell has one different haploid set of chromosomes
DNA
Deoxyribonucleic acid - genetic material found in the chromosomes in the nucleus of cells
gene
short piece of DNA that codes for a specific protein, codes for a characteristic
structure of DNA
molecule formed from two strands twisted together in a double helix
DNA bases
A(adenine) T(thymine)
C(cytosine) G(guanine)
what hols DNA strand together
weak hydrogen bonds
DNA structure
DNA is a polymer made of monomers called nucleotides joined together
Phosphate (circle)
deoxyribose sugar (pentagon) Base (square)
when gametes fuse they form a
diploid zygote
allele
different versions of the same gene
chromosomes of the same pair have
the same genes in the same order
heterozygous
different alleles of the same gene
homozygous
same alleles on both chromosomes
genotype
shows the alleles in each individual - punnet squares
phenotype
the characteristics that are produced - punnet squares
dominant
will show when one allele is present in the genotype
recessive
will only show when two alleles are present in the genotype
pedigree analysis
used to study inheritance of dominant and recessive alleles
predict the chance of someone inheriting a specific allele
carriers
have one copy of a faulty allele
genotype XX
female chromosomes
genotype XY
male chromosomes
at fertilisation there is an equal chance of
producing a male or a female
variation factors can be
genetic and environmental
phenotypic features
hair colour, eye colour
caused by many genes
genetic variation
hair colour
eye colour
environmental variation
scars
ability to ride a bike
genetic and environmental variation
weight
skin colour
mutation is created
when subsequent bases in a gene is changed
mutations however
- most genetic mutations have no effect on phenotype
- some have a small effect
- a single mutation rarely, significantly affects the phenotype
a mutation may cause
- a large change in protein produced
- a small change
- no change
mutation in non coding DNA can
increase or decrease ability of RNA polymerase to bind to DNA
The Human Genome Project
collaboration between scientists to decode the human genome (order of bases on all human chromosomes)
- completed quickly due to number of scientists working at the same time
- published in 2003
- used for new medicines
advantages of the human genome project
- alerting people they are at risk of particular diseases
- distinguishing between differences in diseases like leukaemia, some drugs are beneficial for different forms
- allowing doctor to ‘tailor treatments’ for some diseases to the individual
disadvantages of the human genome project
people who were at risk of certain disease like cancer could have claimed more life insurance
- may not be useful to tell someone the risk of a condition with no cure currently
