genetics and behaviour- lecture 2

Question 1

early thoughts on genetics

Answer 1

acquired characteristics can be inherited

Question 2

what did darwin say about genetics

Answer 2

characteristics inherited due to pangenesis

Question 3

what is pangenesis

Answer 3

the body produces gemmules which travel to sex organs and pass on characteristics to further generations
BUT children arent an exact copy of parents- some features identifiable as coming from 1 parent but others appear to be a blend

Question 4

who is gregor mendel

Answer 4

• an augustine monk
• carried out a series of experiments but only really acknowledged in 1900s
• discovered dichotomous traits and true breeding lines
• pea plant experiment

Question 5

what are dichtonomous traits

Answer 5

traits that occur in one form or another not both e.g. pea plant seeds= brown or white

Question 6

what are true breeding lines

Answer 6

pure interbreeding always produces the same trait e.g. brown seed plant= brown seeds

Question 7

mendelian genetics

Answer 7

• certain factors are transmitted from parent to offspring- mendel suggested these were directly responsible for physical traits
  key terms= genotype, phenotype, homozygous, heterozygous
  use punnet square to understand simple genetic inheritance

Question 8

genotype

Answer 8

genetic code

Question 9

phenotype

Answer 9

the physical trait- affected by environment

Question 10

homozygous

Answer 10

2 identical trait genes

Question 11

heterozygous

Answer 11

2 different trait genes

Question 12

mendels legacy

Answer 12

• genes- the factors that are passed on
  2 genes for every dichotomous factor
  organisms randomly inherit 1 gene from mother and father
  combination determines genotype and phenotype for the trait
  1 of genes can be dominant e.g. brown eyes= B, blue eyes= b

Question 13

DNA structure

Answer 13

1 phosphate group, pentose sugar, nitrogenous base
adenine, thyamine, cytocine, guanine
genetic base pairing- A+T G+C
sequence of 3 bases- codon
each codon codes for 1 amino acid
completed code is the gene
gene is located on chromosomes

Question 14

how many genes in nucleus

Answer 14

34000 housed in 46 chromosomes (23 pairs)- 1 from each pair
22/23 pairs are autosomal- determine all traits apart from sex
23rd pair determines phenotypic sex

Question 15

why are males more suceptible to sex linked diseases than females

Answer 15

• females receive 2x chromosomes so they get 2 doses of sex linked genes, males only recieve 1 (comes from the mother)
• if female has harmful reccesive gene on 1 chromosome they usually have dominant normal gene to counteract it
• males more likely to recieve defect as only has 1 X

Question 16

inheriting haemophelia

Answer 16

females often carry the gene
if males have this gene, it shows on the phenotype

Question 17

genes to behaviour

Answer 17

genes dont supply every detail of an individual
they initiate particular developmental pattern that may/may not be activated depending on many possible environmental and physiological changes

Question 18

what is heritability

Answer 18

the degree to which differences in characteristics are due to genetic differences
this takes a value between 0 and 1
the scientific study of heritability is called behavioural genetics

Question 19

methods in behavioural genetics

Answer 19

1. artificial selection
2. family studies

Question 20

artificial selection

Answer 20

tryon (1940) trained rats to find their way through a maze
he selectively bred the fastest and the slowest
over generations, 2 clear groups emerged

Question 21

family studies

Answer 21

we can take specific family membersand compare their behaviours with people of differing genetic relations
if characteristics are more common in closely related individuals then it could have a genetic component
some studies have compared MZ twins with DZ twins, because MZ twins are genetically identical they should show greater similarities (concordance) in their behaviours than DZ

Question 22

concordance in MZ twins

Answer 22

MZ twins show high concordance rates for many physical and behavioural characteristics
BUT
twins reared in same environment which can affect their behaviours
MZ raised apart should still be more similar than non identical raised together
BUT no behaviour has heritability 1 so genes and environment interact to form behaviours