Chapter 2: Heredity

Question-and-answer flashcards covering key concepts from Chapter 2: Heredity, including fundamentals of genetics, chromosomal abnormalities, autosomal recessive and sex-linked disorders.

Why do we talk about heredity in a psychology class?

Because genes influence development, behavior, intelligence, and risk for psychological disorders; psychology studies how biology and environment interact.

How many chromosomes are in human cells?

46 total (23 pairs).

What is a zygote?

The first cell formed from sperm and egg, containing all 46 chromosomes.

What are genes?

Segments of DNA on chromosomes that code for traits (physical and psychological).

What’s the difference between single-gene and polygenic traits?

Single-gene traits are controlled by one gene (rare, either/or outcome). Polygenic traits are influenced by many genes and show up on a spectrum (most traits).

Which is more common: single-gene or polygenic traits?

Polygenic traits.

Why is King Henry VIII relevant to heredity?

People blamed his wives for not producing sons, but it’s the father’s sperm that determines sex (X or Y chromosome).

What is a karyotype?

A picture of chromosomes arranged in pairs, used to detect abnormalities.

What are autosomes vs. sex chromosomes?

Autosomes = first 22 pairs (control most traits). Sex chromosomes = 23rd pair, determine biological sex (XX female, XY male).

What causes Down Syndrome?

An extra copy of chromosome 21 (Trisomy 21).

What are characteristics of Down Syndrome?

Flattened face, almond-shaped eyes, short neck; heart, hearing, vision problems; intellectual disability and delayed speech.

What is the biggest risk factor for having a baby with Down Syndrome?

Maternal age (especially over 35).

What is Klinefelter Syndrome (XXY)?

Males with an extra X chromosome; symptoms include tall stature, low testosterone, small testes, sometimes learning problems.

What is Turner Syndrome (X)?

Females missing an X chromosome; symptoms include short stature, webbed neck, underdeveloped ovaries, infertility.

What is Triple X Syndrome (XXX)?

Females with an extra X chromosome; often no major symptoms, may be taller, mild developmental delays.

What is XYY Syndrome?

Males with an extra Y chromosome; taller, sometimes learning difficulties.

What is an allele?

A different version of a gene.

What does dominant mean?

Only one copy of the allele is needed for the trait to appear.

What does recessive mean?

Both copies must be recessive for the trait to appear.

What does homozygous mean?

Having two of the same alleles (AA or aa).

What does heterozygous mean?

Having two different alleles (Aa).

What is genotype vs. phenotype?

Genotype = genetic makeup. Phenotype = physical expression of traits.

What is Mendelian inheritance?

The predictable passing of traits according to dominant and recessive allele rules (Punnett squares).

What must happen for a baby to inherit an autosomal recessive disorder?

Baby must inherit two recessive alleles (one from each parent).

Do autosomal recessive disorders affect males and females equally?

Yes.

What is PKU?

A disorder where the body can’t metabolize phenylalanine; untreated it causes brain damage, treated with a special diet.

What is Sickle Cell Disease?

Abnormal hemoglobin makes red blood cells sickle-shaped; causes pain, fatigue, organ issues; common in African and Mediterranean groups.

What is Tay-Sachs Disease?

Nervous system degenerates due to missing enzyme; usually fatal in early childhood; more common in Ashkenazi Jewish populations.

What are sex-linked genetic abnormalities?

Disorders carried on the X chromosome.

Do sex-linked genetic abnormalities affect males and females equally?

No — males are more affected because they only have one X chromosome (hemizygous). Females can be carriers.

What is red-green color blindness?

An X-linked recessive disorder where individuals cannot distinguish red and green shades.

What is hemophilia?

An X-linked recessive disorder where blood doesn’t clot properly, leading to excessive bleeding.

If a mother is a carrier for an X-linked recessive disorder and the father is unaffected, what are the chances for her children?

Sons: 50% chance of having the disorder. Daughters: 50% chance of being carriers.