Genetics & Heredity

Lifespan Growth & Development Exam 1 (2/24/26)

Somatic cell:

The body cells in an organism except the reproductive cells.

Gamete Cell:

The reproductive cells that carry half the genetic information of an organism.

What is a zygote?

The first cell formed when a sperm fertilizes an egg.

What is significant about the 23rd chromosome?

They are the sex chromosomes

What are our autosomes?

The body chromosomes

Phenotype:

The observable traits or characteristics of an individual

Genotype

an individual’s genetic makeup or Genetic blueprint

What is a recessive gene?

the phenotype when an individual has two copies of that gene. (bb)

What is a carrier?

an individual who carries a recessive gene for a trait or disorder but does not show it in their phenotype because they also have a dominant allele that masks it.

What is a dominant gene?

A gene whose trait will appear in the phenotype even if only one copy is present. (Bb)

What is genetic counseling?

A process where trained professionals help individuals or families understand their genetic risks, inheritance patterns, and the likelihood of passing on certain traits or disorders.

What is the Human Genome Project?

An international research effort to map and sequence all the genes in human DNA.

Why are men more likely to suffer from X-linked diseases?

They have only one X chromosome so there is no second X to compensate

Give an example of an X-linked disease:

Color blindness (red-green)

Hemophilia

Describe the symptoms of it: Color Blindness (Red Green)

Difficulty distinguishing red from green shades.

Confusing brown, orange, or yellow with certain reds or greens.

Trouble identifying traffic lights by color (relying on position instead).

Color-related tasks (e.g., reading color-coded maps or charts) can be challenging.

Some people may see colors as duller or less vibrant.

The red and green cones in the eyes don’t function properly.

Describe the symptoms of it: Hemophilia

Excessive bleeding from cuts or injuries.

Spontaneous bleeding into joints and muscles.

Frequent nosebleeds or gum bleeding.

Easy bruising even from minor bumps.

Prolonged bleeding after surgery or dental work.

a genetic disorder affecting blood clotting, usually caused by a deficiency of clotting factors.

What is PKU?

a genetic metabolic disorder where the body cannot break down the amino acid phenylalanine.

How is PKU acquired?

Is acquired genetically, autosomal recessive disorder.

What is sickle cell anemia?

a genetic blood disorder in which the body produces abnormally shaped red blood cells in the shape of a sickle or crescent.

How is Sickle Cell Anemia acquired?

Is acquired genetically, autosomal recessive Disease

What is Huntington’s Disease?

a genetic neurodegenerative disorder that causes progressive breakdown of nerve cells in the brain, leading to movement, cognitive, and psychiatric problems.

How is Huntington’s Disease acquired?

a mutation in the HTT gene on chromosome 4.

When do symptoms emerge for Huntington’s Disease?

Symptoms usually appear between ages 30–50 but can occur in juveniles.

What is cystic fibrosis?

a genetic disorder that affects the exocrine glands, leading to the production of thick, sticky mucus that can damage the lungs, pancreas, and other organs.

What is Tay Sachs disease?

a genetic neurodegenerative disorder caused by the accumulation of GM2 ganglioside in neurons, leading to progressive brain damage.

Monozygotic Twin:

is a pair of twins that develop from a single fertilized egg that splits into two embryos.

Dizygotic Twin:

A pair of twins that develop from two separate eggs fertilized by two separate sperm cells.

What does concordance rate mean?

The probability that both individuals in a pair of often twins will likely share a particular trait or disease if one of them has it.

What is the diathesis stress theory?

explains that psychological disorders or diseases develop due to the interaction of a genetic vulnerability and environmental stressors.

What does the field of epigenetics study? (Provide an example)

the study of how gene expression is regulated by factors other than changes to the DNA sequence itself.

Ex: Tobacco smoke can add methyl groups to tumor-suppressor genes, turning them off and increasing cancer risk, even though the DNA sequence itself hasn’t changed.

Identify the abnormalities in the sex chromosomes & symptoms/markers of: Klinefelter’s

Karyotype - extra X in males (47, XXY)

Tall, small testes, sparse hair, gynecomastia, infertility, low testosterone, mild learning issues.

Identify the abnormalities in the sex chromosomes & symptoms/markers of: Turner’s Syndrome

Missing X in females → 45, X

Short stature, webbed neck, broad chest, lack of ovarian development → infertility, delayed puberty

What is Trisomy 21?

A genetic condition in which a person has three copies of chromosome 21 instead of the usual two which causes Down syndrome

What are the major signs of Trisomy 21?

flat face, slanted eyes, single palm crease, short stature, low muscle tone, heart defects, and mild-moderate intellectual disability.

What are stem cells?

Are unspecialized cells that have the unique ability to self-renew & differentiate.

What is In Vitro Fertilization (IVF)?

a medical procedure to help people conceive a baby by fertilizing an egg with sperm outside the body in a laboratory.

Amniocentesis:

a prenatal test used to detect genetic or chromosomal disorders in a developing baby.

Chorionic Villus Sampling (CVS):

a prenatal test used to detect genetic or chromosomal disorders in a developing baby, similar to amniocentesis but done earlier in pregnancy.

Ultrasound:

a medical imaging technique that uses high-frequency sound waves to create images of structures inside the body.

Nuchal Translucency:

a prenatal screening test that measures the fluid at the back of a fetus’s neck to assess the risk of certain chromosomal conditions.

Maternal blood analysis:

a prenatal screening test that examines a pregnant woman’s blood to assess the risk of certain genetic or chromosomal conditions in the fetus.

How they are performed - Amniocentesis

A small amount of amniotic fluid (which contains fetal cells) is withdrawn from the uterus using a needle, guided by ultrasound.

How they are performed - CVS

A small sample of placental tissue (chorionic villi) is taken, either through the cervix or the abdominal wall, usually guided by ultrasound.

How they are performed - Nuchal Translucency

The ultrasound measures the thickness of the fluid-filled space at the back of the fetal neck.

How they are performed - Maternal Blood Analysis

A blood test in pregnancy to screen for Down syndrome, trisomy 18, and neural tube defects.

Their use as a prenatal test - Amniocentesis

Tests for conditions like Trisomy 21 (Down syndrome), Trisomy 18, cystic fibrosis, and other genetic disorders.

Their use as a prenatal test - CVS

Detects chromosomal disorders (like Trisomy 21, Trisomy 18) and certain genetic conditions.

Their use as a prenatal test - Nuchal Translucency

Screens for chromosomal abnormalities like Trisomy 21 (Down syndrome), Trisomy 18, and Trisomy 13.

Can also indicate potential heart defects.

Their use as a prenatal test - Maternal Blood Analysis

Trisomy 21 (Down syndrome)

Trisomy 18

Neural tube defects - spina bifida