B14 Flashcards
(51 cards)
what is an allele
different form of the same gene
what is phenotype
the physical appearance caused by inherited information
what is variation
difference in characteristics in or between species
what are the genes of a female gamete
xx
what are the genes in a male gamete
xy
where does genetic variation arise from
mutations
how does a new phenotype occur
mutations happen continuosly in the body during cell division. However most mutations do not alter the phenotype. Most influence the phenotype but do not determine the phenotype
how can a phenotype be influenced
- differences in the genes of organisms caused by mutations and sexual reproduction
- differences in the environmental conditions organisms live in
- or both
how are identical twins born
a feertillised egg splits in to and grow independently which means the twins have the same DNA so the differences have to some from the environment
what are some phenotype variation caused by genes
- eye colour
- natural hair colour
- nose shape
- blood type
- ear lobe shape
what are some phenotype variation caused by the environment
- hair lenght
- accents
- tatoos
- scars
what are some factors affected by genes and the environment
- weight
- skin colour
- being athletic
how are non-identical twins formed
when 2 sperm fertilise 2 seperate eggs at the same time
what is the theory of evolution
- 3 billion years ago simple life organisms evolved by natural selection causing variation
what is evolution
a change in inherited characteristics of a population over time through natural selection
when is a new species formed
when population of one species has become so different in phenotype they can no longer breed to produce fertile offspring
what is a species
a group of similar organisms which can reproduce to have fertile offspring
what is natural selection
when a species shows variation causing it to be better adapted at surving allowing to breed more successfully and pass on its genes
are mutation always negative
no some could be positive or not positive at all and fatal
what factors can cause mutations
- x-rays
- UV light
- Radiation
- Chemicals
what is selective breeding
when humans breed plants and animals to get desired characteristics
does selective breeding fertil offspring
no, it produces infertile offspring
what are the steps in selective breeding
1- parents with desired characteristics are choosen from a population
2- they are bred together
3- from teh offspring thoose with desirable characteristics are bred
4- this happens over many generations untill all the offspring show desired characteristics
what are cons of selective breeding
- health problems
- body growing soo fast that the legs can not support the large bodies
- reduction in the gene pool
- organisms can have harmful gene defects cause of the reduced gene pool
- organisms are vulnerable to new diseases