Chapter 3: Nature and Nurture Working Together Flashcards
What was Darwin’s problem and how did Mendel help?
blended inheritance. Mendel proposed particulate inheritance, which explained dominant and recessive genes.
What is the modern synthesis?
Darwin’s NS paired with Mendel’s particulate inheritance. Evolution is a change in relative allele frequencies over generations.
Define a gene
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
In the human population, about ____ of loci have a fixated allele.
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.
What are three things done by DNA?
it stores information, replicates, and transcribes protein
How does protein’s shape determine function?
local pH, temperature, the type of cell transcribed in
the relationship between DNA and protein is not deterministic but
it is designed to be influenced by the environment right from the start
What is genetic drift?
the change in gene frequency because genes passed down from one generation to the next are selected randomly, not evenly
What is the founder effect?
a special case of genetic drift when a small subset of a population is used to establish a new colony.
What is a bottleneck?
the population is drastically reduced for at least one generation; genetic diversity is lost bc alleles can be removed from the gene pool forever
Define epigenetics
the study of the regulation of gene expression due to chemical modifications of DNA that are reversible across generations
3 mechanisms of epigenetics
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)
Polygenetic inheritance and pleiotropy
when multiple genes influence a trait versus when multiple traits are influenced by a single gene
Genomic Imprinting
- 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)
Meiosis
- 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
Prenatal development (this is a long one)
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
Placenta
- 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
Differences between mono- and dizygotic twins?
Mono- one zygote, identical genomes
Di- 2 zygotes, different genomes
Are identical twins really identical?
- share placenta but usually have different amniotic sacs, meaning different uterine environments
- similar factors include IQ, 20 personality measures, birth weight, congenital anomalies
Nausea during pregnancy
is adaptive. protects fetus from toxins, less likely to miscarry.
Neuronal Development
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
Why do we need synaptic pruning?
to allow for plasticity
What did blended inheritance think about mutations?
denied them. Mutations would fade out of the gene pool over generations, making beneficial ones unable to take over a population
Mutation in somatic versus sex cells…
not passed on; passed on, making it subject to exposure to NS
Cognitive adaptation during pregnancy
pregnant women have better memory for male faces. This helps raise awareness of threats. Increased negativity to unknown people. Organize house in third trimester.
