| what are the 3 factors that cause mutations? | radiation - UV from sun, gamma, X-rays
chemical: reactive oxygen species (pollutants)
biological: bacteria and viruses |
| What are Mendel's laws? (3) | law of segregation: alleles separate when gametes form
law of independence: alleles separate independently
principle of dominance: dominant alleles mask recessive alleles |
| how did Mendel discover these laws? (3) | large number of pea plants were crossed
1) crossed a variety of purebred peas
2) crossed the offspring with each other
3) crosses performed again and again for reliable results |
| How did the results show these laws? | the offspring only expressed 1 allele not a mix (shows dominance) |
| what was the normal ratio expressed in mendel's law? | 3:1 |
| what are the exceptions of mendel's laws? (2) | linked genes: genes located on the same chromosome
some genes show co-dominance or incomplete dominance |
| what are gametes? how are they made haploid? (2) | Haploid cells formed by meiosis
separated into different nuclei in meiosis 1 separating the allele pairs |
| what happens to number of alleles when gametes fuse? | zygote will have 2 alleles for each gene |
| what is an exception to having 2 pairs of each gene? | males sex chromosome only have 1 allele for each gene because XY arent paired |
| what does homozygous mean in terms of genes? | maternal and paternal alleles are the same |
| what does heterozygous mean in terms of genes? | maternal and paternal alleles are different |
| what does hemizygous mean? and what is considered to be hemizygous? | male sex chromosomes because only 1 allele for each gene is located on the chromosome |
| what is genotype? (2) | gene composition for a specific trait can be hetero or homozygous |
| what is phenotype? | observable characteristic of a specific trait determined by genotype and environment |
| what is codominance | when both alleles are expressed equally
Eg: black and white feathers Csmall B CsmallW
CBCW |
| Explain the dominance of ABO blood group | A and B are co-dominant and change the antigen structure
O is recessive and doesnt change the antigen structure
blood group alleles are represented as I smallA IsmallB or i |
| how are genetic diseases caused? | mutations to genes affect cell function |
| what is an example of autosomal recessive disease? | cystic fibrosis |
| what is an example of autosomal dominant disease? | Huntingtons disease |
| what is an example of codominance disease? | sickle cell anaemia |
| what is cystic fibrosis? (5) | autosomal recessive disorder
mutation to CFTR gene on chromosome 7
produce thick sticky mucus which clogs airways and digestive ducts
respiratory failure and pancreatic cysts
heterozygous people will only be a carrier |
| what is huntington's disease? (6) | autosomal dominant disorder
mutation to HTT (Huntingtin) gene on chromosomes 4
has a repeating CAG unit in low amounts (10-25 repeats)
if more than 40 the protein will misfold = neurodegeneration
happens in middle age
symptoms: spasmic movements, dementia |
| what does sex linkage mean? | when a gene controlling characteristic is on a sex chromosome |
| why are sex linked condition usually x linked? what does this mean in terms of who inherits the disease (5) | because the X chromosome is longer and has more genes that arent present in the Y chromosome
some disorders are linked w a particular gender
X linked dominant is more common with females
X linked recessive are more common in males
only females can be carriers of recessive conditions |
| examples of x linked recessive conditions? who are they more common in? | red-green color blindness and haemophilia are more common in males bec they cannot mask the trait with a dominant allele as they only receive one X |
| how are alleles for sex linked traits written? | allele is written in small as a subscript beside the X (Sex chromosome) |
| What is haemophilia caused by? (3) | ability to control blood clotting is impaired
when factor VIII form coagulation factors becomes defective
fibrin cant form so bleeding continues |
| what is red-green color blindness caused by? | caused by mutation to red or green retinal photoreceptors which are on the X chromosome |
| what are the 3 factors that cause mutations? | radiation - UV from sun, gamma, X-rays
chemical: reactive oxygen species (pollutants)
biological: bacteria and viruses |
| what are mutagens? | increase the rate of genetic mutations |
| what were the effects of the nuclear bombing of Hiroshima? when did it happen? (5) | in 1945 at the end of WW11
many people died but less radiation was spread
increased cancer development
less T cells = higher rate of infection
organ specific health effects |
| what were the effects of the chernobyl accident? (3) | in 1986 explosion of reactor core released a lot of radiation
thyroid disease was common bec of radioactive iodine
250% in congenital abnormalities |
| how is autosomal dominant determined? | both parents affects and offspring unaffected
if both parents unaffected = offspring unaffected |
| how is autosomal recessive determined? | both parents unaffects and parents affected = hetero carriers |
| how is X linked dominant determined? | male has trait = all daughter
unaffect mom cant have affect sons
common in females |
| how is X linked recessive determined | if female has all of her sons do as well
more common in males |
