science revision teachers notes T2 W10 Flashcards
What is an allele?
Alleles are variations of a gene
What is a dominant allele?
The allele that is always SEEN
What is a recessive allele?
The hidden Allele
what is a dominant allele represent represented by?
capital letters
what is a recessive allele represented by?
lowercase letters
when are dominant alleles seen?
always
when are recessive alleles seen?
when there are 2 recessive alleles or when there are No dominant alleles
what is a genotype?
A genotype is an individual’s genetic make-up. (Alleles)
what does homozygous mean?
it means an individual has Two identical alleles
what does a Punnett square show ?
the percentage chance of an offspring’s phenotype and genotype
is “B” dominant or recessive?
Dominant
Is “f” dominant or recessive?
Recessive
is BB Homozygous or heterozygous?
Homozygous
R is Red and r is white. what phenotype is Rr?
Red
R is red and r is white. what phenotype is rr?
white
R is red and r is white. what phenotypes is RR?
Red
what sex chromosomes represent a male?
XY
what sex chromosomes represent a female?
XX
If a disease is recessive. is this male affected, unaffected or a carrier? XbY
Affected
If a disease is recessive. is this male affected, unaffected or a carrier? XBY
unaffected
if a disease is recessive. is this female affected, un affected or a carrier? XbXb
affected
if a disease is recessive. is this female affected, un affected or a carrier? XBXb
carrier
if a disease is recessive. is this female affected, un affected or a carrier? XBXB
unaffected
what does a square represent in a pedigree?
male
what does a circle represent in a pedigree?
female
what does a shaded shape mean in a pedigree?
A person affected by a disease
what does an unshaded shape mean in a pedigree?
A person that is unaffected or a carrier
if a line connects two shapes in a pedigree what does this mean?
they mated
what is a mutation?
a permanent change in the DNA sequence
what do mutations create in a population?
new alleles OR new variations of genes
What is a gene pool?
the sum of different alleles in a population
what is allele frequency?
The frequency/percentage of one allele in the population
what is a mutagen?
a substance that increases the rate of mutations
what are 3 main mutagens?
Radiation, Chemical and UV light
what is an example of a radiation mutagen?
x-rays
what is an example of a chemical mutagen?
tabacco
what is an example of a UV mutagen?
The sun’s rays
what is a co-dominance?
when two dominant alleles are both expressed in an individual. This creates patches in colouring.
E.g. white dog + brown dog= Brown and White spotted dog.
what is a carrier?
A person who does not show a disease/have a disease… however, carriers it in their DNA and can pass it onto their children.
what are the 3 stages of natural selection?
- variation
- selection pressure
- adaptation
what are the 3 stages of speciation?
- variation
- isolation
- selection
what is variation?
the amount of different alleles in a population.
E.g. humans can have brown eyes, blue eyes, green eyes.
what is selection pressure?
a change in the environment that causes an allele to have an advantage.
E.g. predation
what is adaptation?
when the “filter” allele in a population becomes more common and allows organisms to be better adapted to survive in their environment.
what is isolation?
the separation of one population into two or more for a long period of time preventing them from mating with other populations.
what are the 2 types isolation?
geographical
climate
what is geographical isolation?
when a land feature separates individual in a population.
E.g. mountains, rivers, canyons
what is a climatic isolation?
when climatic events cause the separation of individuals in a population.
E.g. temperature
what is an example of speciation?
squirrel population in America had varying arm lengths
the grand-canyon isolated/separated the population into 2 groups
the south side squirrel population adapted to tall trees and got longer arms
the north side squirrel population adapted to flat rocky surface and got short arms for running fast.
two new species formed from one.
what is an example of natural selection?
the peppered moth has 2 variations: dark and light. coal production coated trees with black soot.
the dark moths camouflaged with the black soot avoiding predators.
light moths were eaten.
the frequency of dark moths became more common, dark colours moth are better adapted to survive in their environment.
what is artificial selection?
when humans deliberately breed organisms to get desirable traits in offspring.
what is crossbreeding?
breeding two organisms with a different desirable traits to combine them and get both in the offspring.
what is inbreeding?
breeding related organisms together to emphasise a desirable trait in offspring.
what is evolutions?
the permanent change in allele frequency in a population.
what is the theory of evolutions?
the theory that all organisms originate from a common ancestor.
what 2 types of evolution are there?
- convergent
- divergent
what is convergent evolution?
when two organisms have similar structure with the same function, not because of common ancestor. due to common selection pressure (environment).
E.g. Fin or shark and dolphin.
what is an analogous structure?
a characteristics that 2 different species have for the same function, not because of common ancestor. due to common selection pressure (environment)
what is divergent evolution?
when two organisms have similar structure that have been adapted for different functions. these structures come from a common ancestor.
E.g. forearm of cat and human
what is a homologous structure?
A structure that is the same in multiple species however has different functions. these come from a common ancestor.
E.G forearm of cat and human
what is a vestigial structure?
a characteristics in an organism that they have from an ancestor that now has no function.
what are 4 pieces of evidence supporting evolution?
fossils
embryo similarities
comparative anatomy
DNA analysis
how do fossils support evolution?
finding fossils and using carbon dating to ages them have provided an evolutionary timeline showing small changes in one species from their ancestors to current date.
how does embryology support evolution?
the embryos of all vertebrates look remarkably similar. this is not a co-incidence it suggests that they have a common ancestor.
how does comparative analogy support evolution?
vestigial structure in organisms suggests that they are passes on from ancestors and are no longer needed. E.g. wisdom teeth in humans may have been from our herbivores (plant eating) ancestors.
how does DNA analysis support evolutions?
similarities in proteins in DNA suggest that different species are closely related. more similarities= more closely related.
E.g. chimpanzees and humans share similarities in DNA.
what is a heterozygous?
it means an individual has Two different alleles
