Chapter 3: Nature and Nurture Working Together

Question 1

What was Darwin’s problem and how did Mendel help?

Answer 1

blended inheritance. Mendel proposed particulate inheritance, which explained dominant and recessive genes.

Question 2

What is the modern synthesis?

Answer 2

Darwin’s NS paired with Mendel’s particulate inheritance. Evolution is a change in relative allele frequencies over generations.

Question 3

Define a gene

Answer 3

A gene is a functional sequence of DNA that remains across a number of generations for long enough to function as a significant unit of NS

Question 4

In the human population, about ____ of loci have a fixated allele.

Answer 4

2/3. When an allele is beneficial, an adaptation becomes species typical, removing alternative alleles to the point that the single allele is called a gene.

Question 5

What are three things done by DNA?

Answer 5

it stores information, replicates, and transcribes protein

Question 6

How does protein’s shape determine function?

Answer 6

local pH, temperature, the type of cell transcribed in

Question 7

the relationship between DNA and protein is not deterministic but

Answer 7

it is designed to be influenced by the environment right from the start

Question 8

What is genetic drift?

Answer 8

the change in gene frequency because genes passed down from one generation to the next are selected randomly, not evenly

Question 9

What is the founder effect?

Answer 9

a special case of genetic drift when a small subset of a population is used to establish a new colony.

Question 10

What is a bottleneck?

Answer 10

the population is drastically reduced for at least one generation; genetic diversity is lost bc alleles can be removed from the gene pool forever

Question 11

Define epigenetics

Answer 11

the study of the regulation of gene expression due to chemical modifications of DNA that are reversible across generations

Question 12

3 mechanisms of epigenetics

Answer 12

methylation (the addition of a methyl group to the DNA base C)
- Positive relationship b/t education and genome-wide methylation!
histone modification (DNA wrapped around histone coil, if too tight genes cannot be transcribed)
lyonization (when one of two X chromosomes gets packed too tightly, only the other is involved in development)

Question 13

Polygenetic inheritance and pleiotropy

Answer 13

when multiple genes influence a trait versus when multiple traits are influenced by a single gene

Question 14

Genomic Imprinting

Answer 14

• reversible chemical tagging of an allele that alters the likelihood it will be expressed in the phenotype
• a special kind of methylation on the X chromosome
• Mom prepares sex chromosome for a son and dad prepares sex chromosome for a girl (X passed from mom to son will lead to dominant expression of allele because Y is too small to provide complementary/competing alleles)

Question 15

Meiosis

Answer 15

• the process by which sex cells (egg and sperm) are produced
• meiosis I leads to 2 daughter cells and meiosis II leads to 4 daughter cells

Question 16

Prenatal development (this is a long one)

Answer 16

Germinal (conception-2 weeks)

• ends when blastocyst implants in uterus
• blastocyst has three layers- outer becomes skin/hair/nails, middle is muscle/skeleton, inner is heart/digestive system

Embryonic (3-8 weeks)

• 4 wks- head, spine, heart beating, body plan
• 5.5-8 wks- face development
• 6 wks- clearer body plan (head/feet/arms)
• 8 wks- fingers and toes, embryo moving

Fetal (9 weeks-birth)

• 7-12 wks- external genitalia develop
• 12 wks- wiggling toes, sucking thumb, responsive
• 16 wks- mother feels movement
• 20 wks- development of nervous system, digestive, respiratory
• 28 wks- hair, thick skin, premature birth but potentially viable

Question 17

Placenta

Answer 17

• has embryonic DNA
• invades uterine wall and affects mother’s blood vessels so they cannot contract
• takes nutrients from her blood but sends hormones to control her blood pressure and sugar
• genomic imprinting means genes from dad play more of a role in developing placenta

Question 18

Differences between mono- and dizygotic twins?

Answer 18

Mono- one zygote, identical genomes

Di- 2 zygotes, different genomes

Question 19

Are identical twins really identical?

Answer 19

• share placenta but usually have different amniotic sacs, meaning different uterine environments
• similar factors include IQ, 20 personality measures, birth weight, congenital anomalies

Question 20

Nausea during pregnancy

Answer 20

is adaptive. protects fetus from toxins, less likely to miscarry.

Question 21

Neuronal Development

Answer 21

Neurogenesis
- creates neuron. Happens 20 wks after conception.
- 250,000 new neurons/min
Neuron migration (from google- happens 2 months into gestation)
- from brain centre outward to functional location.
Differentiation
- begins 20 wks post conception
- cell size increases and becomes more elaborate

Question 22

Why do we need synaptic pruning?

Answer 22

to allow for plasticity

Question 23

What did blended inheritance think about mutations?

Answer 23

denied them. Mutations would fade out of the gene pool over generations, making beneficial ones unable to take over a population

Question 24

Mutation in somatic versus sex cells…

Answer 24

not passed on; passed on, making it subject to exposure to NS

Question 25

Cognitive adaptation during pregnancy

Answer 25

pregnant women have better memory for male faces. This helps raise awareness of threats. Increased negativity to unknown people. Organize house in third trimester.