B5.1 Inheritance Flashcards
what is variation?
the differences between individuals of the same species - cause by genetic + environmental factors
What is a genotype?
the genes / alleles that you possess - 1 inherited from each mum + dad for each characteristic
What is a phenotype?
how genotype is expressed - physical appearance - can be affected by environment (e.g. hair colour)
Dominant allele
stronger allele - usually darker colour - Capital letter
recessive allele
weaker allele - lighter colour - lowercase letter - only shown in phenotype if no other dominant alleles are present
Homozygous
when both alleles are same for a characteristic - OO, oo, AA, aa, BB, bb
heterozygous
2 different alleles for a characteristic - Ao, Aa, Bb
inherited variation
children inherit characteristics from their parents
Environmental variation
characteristics are affected by surroundings
Discontinuous variation
- distinct categories - e.g. blood group, eye colour, finger prints, tongue rolling
- tends to be qualitative
- controlled by a few genes
- unaffected by environment
- e.g. bar graph
Continuous variation
- no distinct categories (e.g. line graph)
- e.g. height, weight, heart rate, hair colour, finger / leaf length
- tends to be quantitative
- controlled by lots of genes
- strongly influenced by the environment
asexual reproduction advantages
- if parents well adapted to area so will offspring - natural clones
- 1 parent needed - animals don’t need find partner, plants don’t require pollination - doesn’t require gametes
- reproduction = faster - large numbers offspring produced quickly
- many plants do this
asexual reproduction disadvantages
- adverse changes to environment may destroy the species - all organisms affected
asexual reproduction example
- strawberry / spider plant - send out runners over ground - runners sprout roots at various intervals - new plants grow - once new plant is established, runners die + rot away
Sexual reproduction advantages
- variation in offspring leads to adaptations in species - adverse changes in environment will not really affect the species
- organisms that survive (survival of the fittest) can produce more offspring with adapted genes - allowing population to continue
sexual reproduction disadvantages
- requires 2 parents
- reproduction is slower - fewer offspring
how does sexual reproduction work?
when nucleus of sperm cell fuses with nucleus of egg cell - egg is fertilised (zygote) - genes from male + female are in fertilised egg which divides and grows in uterus
what is the diploid number?
46 chromosomes in most human body cells
what cells contain only half the number of chromosomes?
haploid number - gametes
where does mitosis occur?
in all somatic body cells during asexual reproduction - results in 2 genetically identical daughter cells
what does meiosis produce?
gametes - haploid cells
how many cells are produced from meiosis?
4 cells produced - 2 divisions
what is a gene?
a length of DNA that contains the code for a specific protein
what is an allele?
different versions of a gene
where is DNA held?
in chromosomes
what is the female sex chromosome
XX
what is the male sex chromosome
XY - Y is shorter
describe the process of meiosis
- diploid cell - 23 pairs of chromosomes - each chromosome makes an identical copy of itself
- one set of chromosomes goes to each daughter cell
- further cell division - 1 chromosome from each pair goes into each of the 4 sex cells that are made haploid
when does a mutation occur?
when sequence of DNA bases is altered
what may mutations cause?
genetic variants - different versions of alleles
- mutations occur spontaneously
do mutations affect an organisms phenotype?
not normally but it can
are the mutations that cause a change in phenotype harmful?
most are - some are neutral and a few are beneficial
what causes mutations?
some chemicals greatly increase chance of mutations occurring - e.g. ethanol, benzene
- ionising radiation - e.g. UV from sun, x-rays
how can a mutation change an organisms phenotype?
if mutation occurs in gene - DNA bases may be changed, added or deleted
- sequence of bases are changed
- mRNA also changed and order of amino acids may change
- TMT protein produced may fold incorrectly + form a diff shape
- if protein is an enzyme, the reaction would no linger be able to be catalysed
