Problem 1: Birds and the bees

Question 1

Genotype

Answer 1

Genetic material inherited

Question 2

Phenotype

Answer 2

Observable characteristics and behaviors that arise from a combination of our genotype and the environment

Question 3

Chromosome

Answer 3

Chromosomes:
- 23 pairs similar in shape, size, and genetic function (excluding XY).
- 50/50 from both parents.
- The first 22 pairs are autosomes and are homologous (the same) and the 23rd pair is the sex chromosome (XY)

Question 4

DNA

Answer 4

Double helix molecule connected by nucleotide
- Adenine
- Thymine
- Cytosine
- Guanine
A and T bind together, and C and G too.

Question 5

Homozygous vs Heterozygous

Answer 5

Homozygous: equal alleles passed on from both parents.
Heterozygous: alleles differ between parents.

Question 6

Conception

Answer 6

Fertilization > ovum > uterus > fallopian tube > fertilized by sperm > zygote

Question 7

Mitosis (cell division)

Answer 7

• From 1 to 2, then 2 to 4, then 4 to 8, etc.
• Chromosomes split > duplication of the chromosomes (23 to 46) > they move to opposite sides > division of the cell (identical sets)

Question 8

Meiosis (cell division)

Answer 8

• Only for sex chromosomes (germ cells)
• They produce gametes
• Duplication of the 23 chromosomes (46) > crossing-over > new unique hereditary combination
• Independent assortment: millions of different combinations.

Question 9

Monozygotic vs Dyzygotic twins

Answer 9

Monozygotic: 100% identical, one zygote split into two identical cells.
Dygotic: Fraternal, two zygotes from two sperms, 50% identical.

• 22 out of the 23 chromosomes are the same in both females and males.
• The 23rd chromosome defines sex: Males: XY, Females: XX

Question 10

Single-gene inheritance

Answer 10

Characteristics influenced by one pair (one allele from the mother, one from the father).
- Dominant vs recessive traits.

Question 11

Co-dominance inheritance

Answer 11

Phenotype of the gene is a compromise between two dominant genes.

Question 12

Sex-linked inheritance

Answer 12

• Traits located on the X sex chromosomes.
• More common in Males (females counteract the traits by having two X chromosomes unless the allele is dominant in both).

Question 13

Hereditary disorders: congenital defects

Answer 13

• Effects present at birth but not detectable right away.

Question 14

Chromosomal abnormalities: Sex chromosomes (Poly X and Poly Y)

Answer 14

1. Poly X: 1 in 1000 female births, fertile, low IQ, normal phenotypically
2. Poly-Y: 1 in 1000 male births, fertile, low sperm count, normal phenotypically.

Question 15

Chromosomal abnormalities: sex chromosomes (Klinefelter’s syndrome - males)

Answer 15

• 1 in 1000 births, XXY, feminine traits, phenotypically male, sterile, poor cognitive abilities.

Question 16

Chromosomal abnormalities: sex chromosomes (Turner’s syndrome XO)

Answer 16

• 1 in 2500 births (females)
• Sterile, normal IQ, one chromosome is missing.

Question 17

Chromosomal abnormalities: sex chromosomes (Fragile X syndrome)

Answer 17

• Anomaly in the X chromosome.
• Common in males more than females, normal, prominent ears/legs, etc.

Question 18

Chromosomal abnormalities: autosomes

Answer 18

1. Down syndrome: extra part of a 21st chromosome (failed to disconnect during meiosis). Intellectually impaired, spokes problems, protruding tongue. 1 in 800 births.

Question 19

Genetic abnormalities: Phenylketonuria (PKU)

Answer 19

1 in 10,000/20,000 births, lack of enzymes to digest food, mental retardation, etc.

Question 20

Genetic abnormalities: Huntington’s disease

Answer 20

• Stops the brain from working over time.
• 1 in 18,000/20,000 births
• Inherited from a dominant allele
• 50% chance for children
• Symptoms: depression, poor motor skills, premature deaths, starts at 40.

Question 21

Genetic abnormalities: Sickle cell anemia

Answer 21

1 in 500 births, abnormal red blood cells, inefficient distribution of oxygen.

Question 22

The prenatal stages: conception

Answer 22

• Begins with fertilization.
• Once every 28 days, an ovum is released from one of the two ovaries and one of the two fallopian tubes is retracted.
• The ovum-released site, the corpus luteum, produces hormones that prepare the uterine wall for conception.
• The males’ testicles produce sperm that develop a tail that swims up the female reproductive system to the fallopian tubes where conception happens.
• Prenatal development starts with conception, lasts around 38 weeks, and can be divided into three periods:
  1. The zygote period
  2. The embryo period
  3. The foetus period

Question 23

Period of the Zygote

Answer 23

• The first two weeks.
• Germinal or zygote period.
• Zygote is a fertilised ovum.
• The zygote moves from the fallopian tubes to the wall of the uterus and cell division (mitosis) takes place.
• The cell division creates two parts:
  1. the Blastocyst: a group of 60 to 70 cells that form a hollow, fluid-filled ball. The inner cells are called the embryonic disk, which will become the new organism.
  2. The trophoblast: the outer layer of cells that provide the embryo with nutrition and protection.
• Implantation also takes place (7th and 9th day): the blastocyst attaches itself to the uterine wall where it grows. Some structures form.

Question 24

Structures formed during implantation: Pericarp

Answer 24

trophoblast multiples rapidly to form pericarp.
- protection layer

Question 25

Structures formed during implantation: Amniotic fluid

Answer 25

The fluid protects the organism from impact, regulates temperatures, and provides a weightless environment that facilitates movement.

Question 26

Structures formed during implantation: Yolk sac

Answer 26

- Produces blood cells until the liver, spleen, and bone marrow are mature enough to take over.

Question 27

Structures formed during implantation: Chorion

Answer 27

- Protective membrane through which the placenta forms. - It contains small blood cells that adhere to the uterine wall.

Question 28

Structures formed during implantation: Placenta

Answer 28

- Ensures transfer of nutrition and oxygen to the organism and takes care of waste removal. - Forms a membrane through which the substances can be exchanged without the blood of the mother and the child mixing.

Question 29

Structures formed during implantation: Umbilical cord

Answer 29

- The connection between the placenta and the organism. - It contains one large vein that delivers blood with nutrients. - It also contains two arteries that carry away waste products.

Question 30

Period of the Embryo

Answer 30

- Between 3rd and 8th weeks after fertilization. - Rapid prenatal changes take place - Groundwork for internal organs and body structures. - The supporting systems, such as the amnion, umbilical cord, and placenta, as well as the organs continue to develop. - The embryo is now very sensitive to changes in the environment. - In the last half of the first month, the embryonic disk forms three layers of cells. 1. The ectoderm: the nervous system and skin - Forms a neural tube that begins to swell to form the brain at around 3.5 weeks. 2. The mesoderm: the muscles, bones, circulatory system, and other internal organs. 3. The endoderm: the digestive system, lungs, urinary tract, and glands. - During the second month, eyes, ears, nose, jaw, and neck are formed. Arms, legs, fingers, and toes as well. The intestines grow, as well as the liver and spleen.

Question 31

Period of the fetus

Answer 31

- From the 3rd month to birth - Organs, muscles, and the nervous system begin to organize and become connected. - Foetus can move. - Genitals can be identified. - During the second trimester, the mother can experience movement. - Brain weight increases rapidly. - During the third trimester, the fetus reached the age of viability. - Fetus received antibodies from the mother.

Question 32

Sensitive periods of the fetus

Answer 32

1. Central nervous system = whole time 2. Heart = 3.5-9 weeks 3. Arms = 4-9 weeks 4. Eyes = 4.5 onwards 5. Legs = 4-9 weeks 6. Teeth = 7-16 weeks 7. Palate = 7-10 weeks 8. External genitalia= 7.5 onwards 9. Ears = 4-20 weeks

Question 33

Teratogens

Answer 33

Environmental factors

Question 34

Effects of teratogens

Answer 34

- During critical periods of development. - Specific effects on specific organs. - Genotype might counteract its effect. Vulnerability! - The effect of one can intensify the effects of another. - Different teratogens produce the same defect. - The longer the exposure, the higher the intensity of the effect - Sleeper effect: damage appears later in life.

Question 35

Legal and Illegal drug effects: Caffeine

Answer 35

Low birth weight, poor IQ and poor motor control, high risk miscarriage

Question 36

Legal and Illegal drug effects: Alcohol

Answer 36

- 6% of births for alcoholic mothers. - Foetal alcohol syndrome (FAS): a lot of drinking, affects the heart, limbs, face, learning, IQ, ADHD link

Question 37

Legal and Illegal drug effects: Nicotine

Answer 37

- ADHD link, low birth weight, genetic damage, cognitive and social development damage, and respiratory diseases.

Question 38

Legal and Illegal drug effects: Marijuana

Answer 38

Affect growth, low birth weight, genetic damage, cognitive, and social development damage, and respiratory diseases.

Question 39

Legal and Illegal drug effects: Cocaine

Answer 39

Physical and behavioral problems, neural damage, long-term effects

Question 40

Legal and Illegal drug effects: Aspirin/diet pills

Answer 40

Affect fetus > low birth weight, IQ and motor control

Question 41

Environmental toxins + parents' factors

Answer 41

- Pollution, pesticides, radiation, mercury, food additives, cosmetics, lead, etc. - Father's exposure to these also affects the child (genetically). - Age, diet, disorders.