Genetics and Heredity

Question 1

Human life begins

Answer 1

with the union of the mother’s egg cell with the father’s sperm cell

Question 2

Egg cells (4 facts)

Answer 2

• -Once every 28 days an egg cell is released
• -All women’s ova are present at birth (maybe a million)
• -Only 400 will mature and be released between puberty and menopause
• -Ovum is the largest cell in the body

Question 3

Sperm cells (2 facts)

Answer 3

• -Males produce billions of sperm per month, (200-300 million every 3-4 days), from puberty until death
• -Sperm one of the smallest cells in the body

Question 4

Two types of cells

Answer 4

• -Body cells, or somatic: contain 23 pair of rod-like structures, which are the chromosomes
• -Sex cells (ova & sperm): contain 23 (versus 23 pair) of chromosomes each

Question 5

Of the 23 chromosomes in each ova or sperm

Answer 5

One chromosome in labeled the sex chromosome and determines the sex of the offspring

Question 6

Father produces 2 kinds of sperm

Answer 6

X & Y
X sperm are large and stronger
Y sperm are smaller and weaker, but faster

Question 7

XX =

Answer 7

Female

Question 8

XY =

Answer 8

Male

Question 9

Each body cell of 46 chromosomes contains (genes)

Answer 9

Roughly 30,000 genes (units of heredity), includes: –skin pigmentation

• -eye color
• -Some personality traits (shyness, activity level)
• -To some extent, intelligence

Question 10

Genotype

Answer 10

person’s hereditary makeup

• -Your actual genetic makeup
• -All genes inherited from your parents
• -Fixed at conception

Question 11

Phenotype

Answer 11

Physical, behavioral, and psychological features that result from the interaction between one’s gene’s and the environment

• -what we see
• -Manifested characteristics
• -Not fixed - interaction between between the genotype and the environment as one develops

Question 12

Examples of dominant phenotypes

Answer 12

Curly hair, normal hair, dark hair, thick lips, cheek dimples, normal hearing, normal vision, farsightedness, normal color vision, Type A blood, Type B blood, Rh-positive blood

Question 13

Examples of recessive phenotypes

Answer 13

Straight hair, pattern baldness (men), blond hair, thin lips, no dimples, some types of deafness, nearsightedness, red-green color blindness, Type O blood, Rh-negative blood

Question 14

Genes & Diseases - basic info

Answer 14

• -Genes are sometimes responsible for certain diseases & defects
• -In most cases, these disorders are linked to recessive rather than dominant genes
• -If a person has a dominant gene for a disease, it will be manifested in the carrier
• -And individual may be a carrier of a single recessive gene for an abnormality and not know it. It will only show up in offspring if both parents are carriers and pass it on.

Question 15

Huntington’s Chorea

Answer 15

• -Fatal disease that is a progressive degeneration of the nervous system.
• -Associated with a dominant gene.
• -Doesn’t manifest itself until one is 30-40 (maybe 50) years of age

Question 16

Sickle-Cell Anemia

Answer 16

• -Linked to recessive gene
• -Carried primarily by African-Americans
• -10% carry the gene
• -Individuals with one dominant and one recessive allele have sickle-cell trait. In most situations, they are fine, but if they suffer a serious shortage of oxygen, they suffer a temporary, relatively mild form of the disease.

Question 17

Incomplete dominance

Answer 17

Situation in which one allele does not dominate another completely

Question 18

What is an allele

Answer 18

variations of genes
There are different forms of genes known as alleles
-If alleles in the pair of chromosomes are the same, they are homozygous
–If alleles in a pair of chromosomes differ, they are hetrozygous

Question 19

PKU

Answer 19

• -Liver enzyme missing that prevents certain foods from breaking down properly
• -Undetected can lead to MR and brain seizures
• -Can be detected in newborns (blood or urine test) and avoided by special diet

Question 20

Tay-Sacks disease

Answer 20

• -Enzyme disorder where the brain is unable to break down certain fatty substances
• -1st symptoms occur at 6 months
• -Child generally dies before ages 3-5
• -Can be detected but not prevented

Question 21

Downs Syndrome - Trisomy 21

Answer 21

• -Chromosomal disorder
• -Occurs in 1 of every 680 births
• -Extra chromosome on chromosome 21 (3 instead of normal pair of 2)
• -Risk increases with the parents’ age, especially the mother
• -Mother in late 20s - 1 in 1000 births
• -Mother in her early 40s - 1 in 50 births

Question 22

Turner Syndrome

Answer 22

• -Associated with the Sex Chromosome
• -1 in 2500 - 5000 females is missing an X sex chromosome (XO)
• -Most are spontaneously aborted (90%)
• -Survivors have underdeveloped sex characteristics
• -Treatable with estrogen
• -Females are sterile

Question 23

Klinefelters Syndrome

Answer 23

• -Associated with sex chromosome
• -Presence of extra X in males (XXY)
• • 1 in 500
• -Small, underdeveloped testicles
• -Some breast development
• -High-pitched voice
• -Little facial hair
• -many infertile
• -Treatable with testosterone

Question 24

XYY Syndrome

Answer 24

• -“Super males”
• -1 in 1000
• -Taller
• -Lower than average intelligence
• -Tend to be more aggressive (not definitive)

Question 25

Fragile X Syndrome

Answer 25

• -The X sex chromosome is abnormally compressed or broken
• -More common in males
• -Results in mental retardation
• -No symptoms until puberty

Question 26

XXX Syndrome

Answer 26

• -Occurs in about 1 in 1000 newborn girls
• -5-10 girls with Triple X Syndrome are born in the US every day
• -May be taller than average, but typically causes no unusual physical features
• -Most females with Triple X Syndrome have normal sexual development and are able to conceive children.
• -May have delayed motor and language
• -May have seizure or kidney abnormalities

Question 27

Genetics and Autism

Answer 27

There is a genetic flaw linked to autism, study published in New England Journal of Medicine in 2008