Chapter 2: Genes and behavior; genetic similarities

Question 1

The transracial adoption study (Minnesota adoption study) (reported by Scarr and Weinberg, 1983)

Answer 1

A: Investigate if black children adopted by white families performed on IQ tests and school achievement as well as other adoptees.

M: Adoption study, longitudinal, correlational.

P: Sampled 101 adoptive families who have biological children and adopted a transracial child. Some of the adopted children were black and others white. The children were adopted around age 0-2. The children were assessed on IQ and school achievement tests.

R: Showed an increase in IQ scores in black children in white families, and that early adoption resulted in higher IQ scores than late adoption.
However, the correlation between the IQ of adoptive parents and adopted children was lower than the correlation between adopted children and their biological parents, which suggests an influence of genetics as well.

C: Adoption increased cognitive abilities – and an increase in IQ occurs due to environmental factors, but the child’s genetics have a say in how the child responds to the environmental factors.
Also, young adopted siblings had an IQ correlation nearly as high as biological siblings, which contradicts the other findings of genetic factors on cognitive ability (biological parents having correlating IQ to biological child).

E: Ethical considerations?

Question 2

The adolescent adoption study (Minnesota adoption study) (reported by Scarr and Weinberg, 1983)

Answer 2

A: Aimed at investigating how differences in cognitive ability accumulated over years till adolescence.

M: Adoption study, longitudinal, correlational.

P: Participants were adolescents who had been adopted early in the first year of life and spent an average of 18 years in their new families.

R: The IQ correlations of biologically related siblings were similar to the transracial study, but the correlation of adopted children who were together for 18 years was 0.

C: Concluded that the observed results may be due to niche-picking. Young children in the same family are similar to each other, whether they are genetically related or not because they share similar rearing environments.
On the other hand, older adolescents are similar only if they share genes because they may have escaped the influence of the family and can select their own environment.
Genetically related people become more similar with age.

E: Ethical considerations?

Question 3

Genotype

Answer 3

An organism’s genotype is the set of genes in its DNA responsible for a particular trait. It is an organism’s full hereditary information and it represents its exact genetic makeup — the particular set of genes it possesses.

Question 4

Phenotype

Answer 4

An organism’s phenotype is the physical expression of those genes in a genotype – an organism’s actual observed properties, such as morphology, development, or behavior.

Question 5

4 methods for studying the influence of genotype on behavior

Answer 5

Twin studies: studying dissimilarities between identical twins.

Family studies: comparing relatives on a broader scale and studying genetic relatedness.

Adoption studies: comparing adopted children to their adoptive parents and siblings, as well as their biological parents and siblings.

Molecular genetics: using technology to study alleles of genes and using genetic mapping to identify them.

Question 6

The falconer model (formula)

Answer 6

a mathematical formula that is used in twin studies to estimate the relative contribution of genetics vs. environment to variation in a particular trait[phenotype] (that is, the heritability of the trait) based on the difference between twin correlations. Assumes that phenotype is comprised of three influences: genetics, shared and individual environment.

Question 7

Niche-picking

Answer 7

the phenomenon when genetic predisposition causes people to choose environments that complement their hereditary and as a result start to affect their behavior.

Question 8

Bouchard and McGue (1981)

Answer 8

aimed at studying IQ relations between relatives. Studied twins – MZ twins that are together are likely to have the highest IQ correlation, but that the correlation cannot be perfect as the environment also influences IQ. They found that intelligence is to a large extent genetically inherited.
Limitations to the study: the assumption that similarity between MZ twins apart is solely due to genotype is limited, in that they could not have been separated immediately after birth (experienced some months together), they could have grown up in similar environments, and shared a common prenatal environment.
Additionally, twin studies have the following limitations: they are rare (problems with replicability), they are not easy to generalize, and the physical appearances of the twins can affect how the environment responds to them and as such affect the study.

Question 9

Kendler et al (2015)

Answer 9

aimed at studying the additive influence on siblings where one stayed at home and the other adopted. There was a correlation between adoptive and biological parents in educational levels. The study suggests that cognitive ability is environmentally malleable, which is seen in that there is a correlation increase between adopted children and on the educational level of adoptive parents.

Question 10

Alleles

Answer 10

A gene is a portion of DNA that determines a certain trait. An allele is a specific form of a gene. Genes are responsible for the expression of traits. Alleles are responsible for the variations in which a given trait can be expressed.

https://www.google.com/search?q=alleles+psychology+definition&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiy__-hwYDmAhUCmIsKHe_zCn4Q_AUoAXoECAwQAw&biw=1745&bih=852#imgrc=7RBdivSkpmjjVM:

Question 11

Chromosomes

Answer 11

All cells that have a nucleus contain a set of chromosomes which is a thread-like structure that contains a DNA molecule, which is coiled many times around supporting proteins.

Question 12

DNA (deoxyribonucleic acid)

Answer 12

stores information – it is a code made up of a long sequence of four chemical bases (adenine, guanine, cytosine, thymine) which are paired up making a sequence of base pairs.

Question 13

Bases and base pairs

Answer 13

attached to each sugar is one of four bases–adenine (A), cytosine (C), guanine (G), or thymine (T). The two strands are held together by hydrogen bonds between the bases, with adenine forming a base pair with thymine, and cytosine forming a base pair with guanine.

Question 14

Gene

Answer 14

Genes are the biochemical units of heredity that make up chromosomes. Genes are segments of DNA molecules that code physical features (e.g. eye color) and psychological features (e.g. intelligence).

Question 15

Cell, chromosomes, DNA, bases and base pairs, genes [photo]

Answer 15

https://qph.fs.quoracdn.net/main-qimg-accc03ab09925ef79d3dc94fbfb7f946.webp

Question 16

Gene expression

Answer 16

the process by which the heritable information in a gene, the sequence of DNA base pairs, is made into a functional gene product, such as protein or RNA. The basic idea is that DNA is transcribed into RNA ribonucleic acid, which is then translated into proteins (translation).
There are many mechanisms that can be used by the body to increase or decrease the production of proteins based on the genetic code. These mechanisms are known as regulation of gene expression, and this results in epigenetic changes (deviation in phenotype from the genetic code in DNA)

https://cdn.britannica.com/96/114896-050-3F22219B/Genes-promoter-regions-production-introns-exons-gene.jpg

Question 17

RNA

Answer 17

Messenger Ribonucleic Acid (mRNA) is RNA that encodes and carries information from DNA during transcription to sites of protein synthesis to undergo translation in order to yield a gene product.

Question 18

Weaver et al (2004)

Answer 18

rats raised by mothers who were less nurturing were more sensitive to stress when they became adults; this was linked to the suppression of the glucocorticoid receptor gene, meaning a smaller number of glucocorticoid receptors in the brain and so increased production of stress hormone.

Question 19

Miller et al (2009)

Answer 19

studied gene expression in people raised in poverty vs. wealthy environments. The researchers expected to find suppression of the glucocorticoid receptor genes, but did not; however, they analyzed blood cells and not brain cells.

Question 20

McGowan et al (2009)

Answer 20

conducted post-mortem examinations of brains of 24 individuals who had committed suicide; people who had been abused as a child had more chemicals in their brain cella suppressing the expression of the glucocorticoid receptor gene.

Question 21

Kaminsky et al (2008)

Answer 21

a case study where researchers investigated the role of epigenetic in phenotypical differences between MZ twins; two 49-year-old females, one a war journalist and the other an office manager in a law firm.

The personality questionnaires showed differences; the law twin had a tendency to overreact to minor problems and is more risk-aversive than war twin. Researchers found one gene, the DLX1 gene (responsible for formation of neurons creating a stress center of the brain) and the researchers concluded that DLX1 methylation may play a role in the development of stress responses in MZ twins.

Question 22

Kaminsky et al (2008)

Answer 22

a case study where researchers investigated the role of epigenetics in phenotypical differences between MZ twins; two 49-year-old females, one a war journalist and the other an office manager in a law firm.

personality questionnaires showed differences; the law twin had a tendency to overreact to minor problems and is more risk-aversive than war twin. Researchers found one gene, the DLX1 gene (responsible for formation of neurons creating a stress center of the brain) and the researchers concluded that DLX1 methylation may play a role in the development of stress responses in MZ twins.

Question 23

Cell, chromosomes, DNA, bases and base pairs, genes [photo]

Answer 23

https://qph.fs.quoracdn.net/main-qimg-accc03ab09925ef79d3dc94fbfb7f946.webp

Question 24

Concordance rate

Answer 24

the probability that the same trait will be present in both members of a pair of twins.

Question 25

Prospective studies

Answer 25

A study where researchers watch for outcomes, such as the development of a disease, during the study period and relate this to other factors such as suspected risk. The study usually involves taking a cohort of subjects that are genetically vulnerable to e.g. a disorder and watching them over a long period.

Question 26

Linkage analysis

Answer 26

The statistical method of linkage analysis combines data to identify chromosome regions likely to harbor genes for a certain trait. The researchers examine DNA for polymorphism (genetic variation).