human bio variation and evolution (LESSON 1 HUMAN VARIATION AND EVOLUTION)

species

a group of individuals that can interbreed to produce fertile offspring

allele

different version of the same gene

gene pool

sum of all alleles in a population

population

a group of organisms of the same species living in the same place at the same time

mutation

random, permanent change in DNA sequence, due to mistakes when copied or environmental factors

mutagen

agents known to increase the rate of mutations in DNA

allele frequency def, and why is it useful

• when geneticists study the frequency of alleles in a gene pool for a particular population

• useful to calculate the frequency of a genetic condition in a population

what happens to the gene pool and allele frequency over time and what are some factors that can affect it

the frequency of alleles in a population changes over time (gene pool changes), either through mutations or naturally.

prey=decreases gene pool

immigration of same species = increases gene pool

2 types of mutations

gene and chromosomal

gene mutations

changes to a single gene during replication where traits are changed or destroyed

chromosomal mutations

all or part of a chromosone is affected

5 examples of mutagens

1. carcinogens (cigs)

2. radiation (UV)

3. mustard gas

4. viruses (HPV)

5. sulfur dioxide

6 damages caused by mutagens

1. Resembles proteins and becomes incorporated into DNA

2. Triggers DNA replications errors

3. Lengthens/breaks DNA

4. blocks DNA replication/damages DNA structure

5. chemically reacts with and modifys dna

6. triggers cells with damaged DNA to multiply

2 overalls results of damage caused by mutagens

• results in gene and chromosomal mutations/can affect one gene or a whole part of a chromosone

• results in somatic or germline mutations/mutations can affect individuals or be passed on

induced v spontaneous mutations

induced mutations are caused by mutagenic agents in the environment

spontaneous mutations are caused by random errors in biological processes such as meiosis or mitosis (non-dysjunction)

somatic mutation

• in body cells

• mutation is passed on to daughter cells during cell division

• includes cancerous growth

germline mutation

• in reproductive cells (gametes)

• mutation is passed on the embryo

• parent doesnt have the mutation

• can occur during interphase

4 effect of mutation

missense, nonsense, neutral, silent

missense mutation

causes a change in the amino acid, and therefore in the protein produced

nonsense mutation

changes the base sequence to a STOP codon, meaning the protein will be shorter and unable to fulfil its function

neutral mutations

causes a change in an amino acid, however the amino acid is of the same type and does not change the structure of the protein enough to change its function

silent mutations

does not cause changes to the amino acids therefore the protein is the same. this is possible as most amino acids re coded for by more than one base sequence

point mutation

a change in just one base (nucleotide) of DNA

3 types of point mutation

substitution, insertion, deletion

substitution

nucleotide replaced with another different one

insertion

new nucleotide added to DNA strand

deletion

nucleotide removed from DNA strand

frameshift

occurs when bases are added or removed, resulting in (not always) a different triplet code and amino acid

errors in dna replication (what it results in 2 types and examples)

1. results in gene or chromosome mutations, can affect one gene or a whole part of a chromosome

2. results in somatic or germline mutations/mutations can affect individuals or can be passed on

   eg cancerous cells, sickle cell anaemia, huntingtons, cystic fibrosis

3 diseases that occur as a result of a gene mutation

• albinism

• duchenne (form of muscular dystrophy)

• cystic fibrosis

duchenne

• wasting away of the leg muscles and later the arms, shoulder and chest

• apparent around age 3-5

• death occurs due to failure of respiratory muscles

cystic fibrosis

• mutation of gene on chromosome 7

• recessive condition (inherited from both parents)

• protein which regulates chloride ions across a cell membrane is not produced

• results in salty skin, persistent cough, wheezing, digestive problems
  

4 types of chromosomal mutations

• deletion (chromosome segment lost)

• Translocation (a segments from a chromosome is transferred to another)

• duplication (a segment from one chromosome is transferred to its homologous chromosome, giving it duplicate genes

• inversion (a segment of a chromosone arm is inverted)

non dysjunction ( a type of chromosomal mutation)

when a chromosome pair does not seperate during meiosis

aneuploidy

when one daughter cell has one extra chromosome and another daughter cell has one less the the normal number

cell division (9 points)

• during cell division homologous chromosomes line up

• genetic material is swapped during cross over

• inversions/chromosomes segment reversed

• translocations/section of chromosome attaches t another

• extra chromosomes can be added to cells/cells can lose chromosomes/aneuploidy/non-dysjunction

• gametes produced have faulty chromosomes/incorrect chromosome number

• results in chromosomal mutations/affects whole parts of chromosomes

• results in germline mutations/mutations can be passed on

• EG down syndrome

3 syndrome for trisomy

downs, patau, klinefelters

down syndrome - chromosome it affects and symptoms

• extra chromosome 21

• flat face, small head, short fingers

patau syndrome - chromosome it affects and symptoms

• extra chromosome 13

• mental retardation, extra fingers, small head

klinefelters syndrome - chromosome it affects and symptoms

• extra X (XXX) or Y (XYY) chromosome

• symptoms develop as adults: testes that produce no sperm, breasts enlarge, little body hair

monosomy diseases

cri-du-chat, turners

cru-di-chat syndrome - chromosome it affects and symptoms

• missing portion of chromosome 5

• an infant has problems with its nervous system and larynx (cry like a meowing cat)

turners syndrome - chromosome it affects and symptoms

• only one x chromosome

• short stature, delayed puberty, infertile

how can abnormalities be diagnosed before birth 3 ways

• blood samples

• amniocentesis

• chrorionic villi sampling