B3 GENETICS Flashcards
gametes
egg and sperm cell
fertilisation
sperm cell fuses with egg cell and nuclei combine
zygote
single cell formed by fertilisation
gene
length of DNA coding for a protein
controls your characteristics
genome
all the DNA and genes in an organism
protein
polymer made from amino acids
polymer
long molecule made by chaining together many shorter ones
diploid
a cell with 23 pairs of chromosomes (46 in total)
haploid
a cell with 23 single chromosomes
meiosis
cell division that makes gametes
meiosis stages
DNA replicates cell divides into 2 diploid cells, these divide into 4 haploid daughters
why gametes are different
chromosomes in a pair are slightly different. Different gametes get different combinations of chromosomes
Chromosome
large DNA molecule made into a small package by tightly coiling DNA around a protein
DNA structure
two strands , double helix , complementary base pairs , sugar-phosphate backbone
DNA bases
adenine A thymine T
cystosine C guanine G
complementary base pairs
A pairs with T
C pairs with G
hydrogen bonds
weak force holding the two strands of DNA together
DNA analysis
issues small differences in DNA to determine family relationships or link people to crimes
Allele
different version of the same gene. we have two alleles of each gene
homozygous
we have two copies of the same allele
heterozygous
we have two different copies of an allele
dominant allele
one copy needed for characteristics to show. written as a capital
recessive allele
two copies for the characteristics to show. written as lowercase
genotype
the combination of alleles in an organism
phenotype
the characteristics produced by the alleles
genetic diagram
shows the likelihood of offspring produced by parents with certain genotypes
sex chromosomes
female: XX
male: XY
inheriting sex
all eggs are, X 50% of sperm are X and 50% are Y so 50% of zygotes are XX and 50% are XY
punnett squares
uses the genotypes of male and female gametes to predict the predict the genotyping of the offspring
probability and punnett squares
punnett squares tell you the likelihood of certain offspring not what will actually happen
cystic fibrosis
illness caused by a inheriting two copies of a faulty recessive allele
family pedigree chart
chart showing how genotypes are inherited down through a family
mutation
a change to the bases in a gene
effects of mutation
change the structure of a protein and how it works . sometimes harmless, normally harmful, very rarely beneficial
cause of mutations
mistakes copying DNA during cell division, DNA damage from chemicals or radiation
inheriting mutations
only if they occur in gametes (egg and sperm)
human genome project
project involving many scientists from many countries to find the order of bases in human DNA
how is HGP useful
to tailor drugs to genes , to design better drugs
genetic differences
HGP found 99% of DNA in all people is identical
variation
natural differences between members of a species that affect the chance of survival
genetic variation
variation caused by genes
environmental variation
caused by interaction with the surroundings such as food, climate etc
causes of most variation
a combination of genes and the environment
acquired characteristics
changes caused by the environment during your lifetime, such as losing a leg
continuous variation
can be anywhere within a range , such as height, following a normal distribution
discontinuous variation
can be only one of a few possibilities such as blood type:A,B,AB,O
normal distribution
bell heaped curve with more in the middle and fewer either side
