4. Genetics

Question 1

What is evolution

Answer 1

darin’s theory of natural selection of traits associated with higher rates of survival (fitness)
Social dominance to pass on important characteristics (males) and to produce more and healthier offspring (females)
Different types of mate bonding to increase chances of passing on important characteristics

Question 2

what questions are involved in the dichotomy of thinking?

Answer 2

is it biological and psychological?
Is it nature or nurture?
Is it inherited or learned?

Question 3

what is the complex process of interaction of genes and environment?

Answer 3

1. evolution influences the pool of behaviour-influencing genes available to members of each species
2. Experience modifies the expression of an individual’s genetic program
3. Each individual genes initiate a unique program of neural development
4. Each individual’s genes initiate a unique program of neural development
5. Each individual’s current behavioural capacities and tendencies are determined by its unique patterns of neural activity, some of which are experienced as thoughts, feelings, memories, etc
6. Each individual’s current behaviour arises out of interactions among its ongoing patterns of neural activity and its perception of the current situation
7. the success of each individual’s behaviour influences that likelihood that its genes will be passed on to future generations

Question 4

Menelian Genetics

Answer 4

Mendel studied dichotomous traits in true-breeding lines of pea plants.
Dichotomous traits - occur in one form or another, never in combination
True-breeding lines: interbred members always produce offspring with the same trait

Question 5

what was step 1 in Mendel’s findings?

Answer 5

In the first experimental step, all offspring plants had brown seeds
one parent had two brown seed genes the other had two recessive white seed geners. thus all offspring had one brown and one white gene. Because brown dominant they all had brown seeds
the dominant gene therefore overwrites the recessive gene

Question 6

What was step 2 of mendel’s findings?

Answer 6

A cross between the first generation offspring, 75% of the offspring had brown seeds and 25% with white

each parent had one brown gene and one white gene. therefore 25% of offspring had two brown genes, 50% had one brown and one white and 25% had two white

Since brown genes dominant 75% had brown

the genetic code of the parent plant was mixed - one allele for brown and one allele for white seeds. Hence, 1/4 of the offspring had white seeds (recessive traits show in the homozygous condition of the recessive gene)

Question 7

Alleles

Answer 7

2 genes that control the same trait

Question 8

homozygous

Answer 8

2 identical alleles (BB, ww)

Question 9

Heterozygous

Answer 9

2 different alleles (B,w)

Question 10

what can genes be?

Answer 10

dominant, recessive or intermediate

Question 11

dominant gene

Answer 11

shows a strong effect in either the homozygous or heterozygous condition

Question 12

recessive gene

Answer 12

shoes its effect only in the homozygoys condition

Question 13

phenotype

Answer 13

observable trait

Question 14

genotype

Answer 14

genetic make-up

Question 15

what are genes a unit of?

Answer 15

fundamentally a unit of heredity

Question 16

what is genetic information carried in?

Answer 16

Deoxyribonucleic Acid (DNA) (and RNA)

Question 17

what does DNA do?

Answer 17

DNA is self replicating material that is contained in almost all living organisms.

Question 18

what is a gene compared to DNA?

Answer 18

a gene is a segment of DNA that encodes specific proteins

Question 19

what does DNA look like?

Answer 19

DNA molecules are double strands of nucleotide bases (T, A, G, C) wrapped around each other

A nucleotide (Allele) on strand 1 always pairs with a particular nucleotide on strand 2 (tymine-adenine, guanine-cytosine)

Question 20

How does DNA fit into the nucleus of a cell?

Answer 20

to fit into the nucleus of a cell, DNA is tightly coiled around “spools” (histones). The package of DNA and histones is called Chromatin.. Chromatin gets packed further to form a chromosome. Chromosomes a paired. Chromatid is the exact copy of chromosome during cell devision (sister-chromatid).

Question 21

chromosomes

Answer 21

contain very tightly wound DNA

Question 22

How many chromosomes to humans have?

Answer 22

humans have 23 matched pairs of chromosomes, with an allele on each chromosome (located in same place) 22 autosomes and 1 sex chromosome

Question 23

how do sex chromosomes look?

Answer 23

looks different and carry different genes (sex-linked genes)

Question 24

what do sex chromosomes determine?

Answer 24

mammalian sex: female (2 X chromosomes) and male (1 X and 1 Y Chromosome)

Question 25

how are sex-linked traits controlled?

Answer 25

almost always controlled by X chromosome genes as it is larger and has more genes.

Traits controlled for by X chromosome genes occur more frequently in one sex than the other.

Question 26

dominant traits

Answer 26

more likely in females as twice the chance

Question 27

recessive traits

Answer 27

less likely in females as they need the recessive gene on both X chromosomes (e.g. colour blindness)

Question 28

what are the two important phases of cell division?

Answer 28

meiosis and mitosis

Question 29

meiosis

Answer 29

(reproduction and recombination) whereby chromosomes devide and one copy ends up in the produce gamete; genetic recombination happens through cross-obers

Question 30

mitosis

Answer 30

(replication) during which the DNA strands unwind, each nucleotide attracts its complementary base (floating in nucleus), making two DNA molecules identical to the original)

Question 31

when can mutation occur?

Answer 31

during replication (errors: individual difference)

Question 32

what do genes produce?

Answer 32

genes do not directly produce behaviours. Rather they produce proteins that increase the probability that behaviour will develop under certain circumstances

Question 33

What is an example of genes and behaviour?

Answer 33

Genetic predisposition to a mental disorder does not mean that you will get the mental disorder. There is usually a complex interplay of environment and presence of several predisposing genes required for the mental disorder to surface.

Question 34

How do we get from gene to behaviour?

Answer 34

DNA -> RNA -> Protein -> outcomes such as health, looks, behaviours etc

Question 35

how do genes produce protein?

Answer 35

Gene segment of DNA strands unwind
Messenger RNA (mRNA) syntehsiized from DNA (transcription): by attracting complementary nucleotides
mRNA leaves nucleus and attaches to ribosomes in the cell’s cytoplasm
Ribosomes synthesizes protein according to 3-base sequences (codons) of mRNA (translation)
Transfer RNA transfers the amino acid to ribosomes

Question 36

what are used for the regulation of gene expression?

Answer 36

Enhancers/Promoters
Transcription factors
Epigenetics

Question 37

Enhancers/producers

Answer 37

stretches of DNA that determine whether particular structural genes initiate the synthesis of proteins

Question 38

Transcription factors

Answer 38

proteins that bind to DNA and influence the extent to which genes are expressed (e.g. by controlling enhancers)

Question 39

Epigenetics

Answer 39

the interaction of environment with the actual gene can regulate gene expression

Question 40

The human genome project

Answer 40

Driven by the idea that if we are able to identify variations in the human genome and link it to disease we can easily target medical treatment and be good.
•Development of many new techniques to study human genetics
•Discovery that we only have relatively few genes – 20 000 (same as mice and less than corn)
•Difficulty of discovering that many genes link to disease and that interactions amongst genes are often times hard to sort out. Also, sum of all genetic contribution is often times small.

Question 41

Epigents

Answer 41

Relatively recent research area (even though idea was around for a long time)

Epigenetics is the study of all mechanisms of inheritance other than the genetic code and its expression (epigenetics does not change the sequence of your genetic code)

Question 42

what have epigenetic studies found?

Answer 42

Epigenetic studies have found mechanisms that modify either the histone (histone remodeling) or the DNA (methylation) and other mechanisms acting on RNA.

Question 43

how can epigenetic changes be induced?

Answer 43

Epigenetic changes can be induced by particular experiences (e.g. intense stress)

Question 44

how are epigenetic changes passed?

Answer 44

Epigenetic changes can be passed on to other generations (transgenerational epigenetics)

Question 45

epigenetics across the human life span

Answer 45

What you experience in your lifetime can modify expression of your genetic code, and these changes can be passed down through the generations.

Question 46

what contributes to epigenetic modulation

Answer 46

psychological state
social interactions
alternative medication
therapeutic drugs
microbiome
exercise
financial status
drugs of abuse
Toxic chemicals
disease exposure
Diurnal/Seasonal Correlations
Diet

Question 47

what is the importance of environment for genetics?

Answer 47

Several study approaches can help exemplify the importance of environment to genetic predisposition:
•Studies of disorder with particular genetic contribution (e.g. Phenylketonuria)
•Animal models (i.e. selective breeding)
•Twin studies

Question 48

Phenylketonuria (PKU)

Answer 48

Neurological disorder characterised by intellectual disability, vomiting, seizures, hyperactivity, irritability, brain damage and strange urinal odours
•Pattern of transmission of PKU suggest single recessive gene disorder
•PKU homozygotes lack phenylalanine hydroxylase
•Environmental factor (diet) can significantly reduce health burden of the disorder

Question 49

what was an animal study conducted on genetics and environmental effects?

Answer 49

Rats were trained to run a maze with a food reward when they reached the goal

Step 1: Rats that were more successful running the maze (less mistakes) were bred with each other and those that were less successful (more mistakes) Offspring of successful maze runners were more successful than offspring of unsuccessful maze runners Control: Offspring of successful maze runners reared by unsuccessful maze runners and other way around -> same results

Step 2: Test the two different sets of rats on many different tasks:

• Rats differed in more than one trait
• Successful maze running rats were less fearful

Step 3: Expose different sets of rats to different environments (impoverished and enriched)  Maze-dull rats did not make significantly more errors than maze-bright rats when both groups were reared in an enriched environment. (Adapted from Cooper & Zubek, 1958.)

Question 50

what did twin studies show?

Answer 50

how we share genetic material with out family.
•50% with mother; 50% with father; 50% with full sibling
•Genetic material between non-identical twins: 50%
•Gene material between identical twins: 100%

Question 51

Minnesota study of twins reared apart

Answer 51

• Identical twins more similar than fraternal twins on all psychological dimensions
• All children were raised by middle-class, tightly scrutinised families in highly industrialised countries yielding little differences in environment

Question 52

Epigenetic effects in monozygotic and dizygotic twins

Answer 52

• Monozygotic twins are indistinguishable early in life but accumulate different sets of epigenetic marks throughout life span
• Monozygotic and dizygotic twins accumulate different sets of epigenetic marks in a high concordance rate (i.e. no substantial differences in accumulation between dizygotic and monozygotic twin pairs)

Question 53

Environmental effects in monozygotic twins

Answer 53

Heritability estimate for IQ dependent on environmental conditions – similar to maze-bright and maze-dull rats. Enriched environments more important for IQ than inheritance.