Genetics Study Guide - Child & Adolescent Development

What is the difference between genotype and phenotype?

Genotype: The set of genes an organism carries

Phenotype: The observable characteristics of the organism

What is the difference between dominant and recessive?

Dominant: the allele that will express itself (and will mask a recessive trait)

Recessive: the allele that will only express itself if you inherited a copy from both of your parents (can easily be masked by a dominant trait if you only received a copy from one of your parents)

What is the difference between homozygous and heterozygous?

Homozygous: where you have identical alleles of a gene (AA or aa)

Heterozygous: where you have two different alleles for a gene (Aa)

What is codominance?

where both alleles from your parents are fully expressed, phenotype displays both traits rather than one being dominant over the other (ex: AB blood type)

Give outcomes of transmission of a hereditary disease

If one parent carries the gene but the other does not, there children won’t have the disease but a 50% chance of being carriers, and a 50% chance of having two unaffected genes.

If both parents are carriers, each child has a 25% of inheriting the disease, a 50% chance of being a carrier, and a 25% chance of having two unaffected genes.

Is a son or daughter more likely to inherit hemophilia?

It is more likely for a man to get it, because they only have one X chromosome (and the disease is determined on the X chromosome). They have no chance (like women do) for the other X chromosome to override it. Women are more likely to carry it.

What are the three major methods of studying polygenetic inheritance?

family studies, twin studies, adoption studies

What is a family study?

To compare you with closer vs. more distant family members to see if you are more similar to those with whom you share a greater percentage of genes

What is a weakness of a family study?

You are much more likely to share an environment with people you are related to (could be a confound)

What is a twin study?

Compares MZ (identical) and DZ (fraternal) twins (genes shared are 100% vs. ~50%)

What is a weakness of a twin study?

MZ twins environment is the same, also normally treated the same

What is an adoption study?

Finds out if children are more similar to biological parents (with whom they share genes), or adoptive parents (with whom they share environment)

What is a weakness to an adoption study?

The adoptive homes that children are placed into are often like biological homes (bio moms can have a say in the couple that raises their child)

What are the most common chromosomal abnormalities?

down syndrome, inter-sex (turner’s, klinefelter’s, superfemale, supermale), fragile x

What is down syndrome?

When a child has an additional 21st chromosome (it is higher in geriatric pregnancies and older fathers)

What is turner’s syndrome?

females who only have one x chromsome (X)

What is klinefelter’s syndrome?

males who have an extra x chromosome (XXY)

What is supermale syndrome?

males with more than one extra Y chromosome (XYY)

What is superfemale syndrome?

females with more than one extra X chromosome (XXX)

What is fragile x syndrome?

In males, when the long arm of the X chromosome breaks (can cause intellectual disability)

What are the 5 methods of detecting chromosomal abnormalities?

preimplantation testing, amniocentesis, chorionic villus sampling, quadruple screen, targeted ultrasound

What is preimplantation screening?

In IVF before the zygote is implanted, allegedly you can take a cell from the baby and it isn’t harmed

what is amniocentesis?

this process is done after 16 weeks, a little amniotic fluid is extracted and tested

what is chorionic villus sampling?

this process is done in the 7 or 8 week, some tissue is extracted from the chorion

what is quadruple screen?

tests the mothers blood for 4 proteins (alpha-feto protein, HCG, estriol, inhibin). if comes back high then there might be a neural tube defect or carrying multiples. if comes back low then baby might have downs.

what is a targeted ultrasound?

this process is done in the 18-22 week, looks for gross abnormalities, heart and neural tube defects

what is behavioral genetics?

field that studies the influence of genetic and environmental factors on behavior, cognition, and personality

what is “shared environment”?

a sibling’s common experiences: parent’s personalities, family’s SES and neighborhood

what is “non-shared environment”?

a child’s unique experiences that are not shared with a sibling (ex: parents act differently with different siblings, siblings have different friends and teachers)

What is the epigenetic view?

the theory that development is the result of ongoing, bidirectional interchange between heredity and environment (ex: in prenatal development baby’s genes will become stronger or weaker due to teratogens, and during infancy the baby will still be affected by these factors)

what are the 3 types of heredity/environment correlations?

passive genotype-environment correlations, evocative genotype-environment correlations, active (niche-picking) genotype-environment correlations

what is passive genotype-environment correlations?

bio parents provide a rearing environment for child

what is evocative genotype-environment correlations?

child’s genetically influenced characteristics elicit certain types of environments

what is active (niche-picking) genotype-environment correlations?

when children seek out environments that they would find compatible