3.19

3.19 describe patterns of monohybrid inheritance using a genetic diagram

Monohybrid: one gene (2 alleles)

P₁ x P₁ Monohybrid cross

Parental phenotypes: red and white (P₁)

Parental genotypes:  GG x gg

Meiosis à production of gametes G G g g 

Random fertilisation: 

F₁ cross F₁ x F₁

Phenotype: Red x Red (F₂)

Genotype: Rr x Rr

Meiosis à Gametes: R r R r

Fertilisation:

Monohybrid F₂ ratio     3:1

Genotypes of the F₂: 1RR: 2Rr: 1rr

Phenotype of the F₂: 3Red: 1White

(PREDICTION STATED BY RATIO: F₂ ratio of 3:1)

3.18

3.18 recall the meaning of the terms: dominant, recessive, homozygous, heterozygous, phenotype, genotype and codominance

Phenotype: what we can see, all possible outcomes, red and white petals

Red x Red = Red, White x White = White, Red x White = Red

Dominant: red R

Recessive: white r

Genotype: combination of 2 alleles, the sum total of genes transmitted from parent to offspring

Homozygous: having identical alleles at corresponding chromosomal loci, same alleles RR (red) or rr (white)

Heterozygous: having dissimilar alleles at corresponding chromosomal loci, different alleles Rr (red)

R (dominant) and r (recessive) are alleles.

Codominance: where both parents’ alleles contribute into producing an unusual third phenotype

B – blue petals, genotype BB

W – white petals, genotype WW

B x W = yellow petals, unusual third phenotype BW – CODOMINANCE

B = W both contribute to the phenotype

3.9b

3.9 recall the structure and function of the male and female reproductive systems

Female reproductive organ

Ovary – (a) meiosis occurs here and production of eggs (female gametes)

Oviducts (fallopian tube) – (b) carry eggs to the uterus, location of fertilisation

Uterus – (c) the centre, wall of uterus, made of muscle,

stretch to accommodate pregnancy, contract during birth

Lining of uterus – (g) develops the fertilised egg à embryo, placenta implanted here

Uterus space – (d) sperm cells and egg cells move, embryo develops à unborn child

Cervix – (e) entrance to the uterus

Vagina – (f) collects the sperm cells and allows them to pass through the cervix into the uterus

Before pregnancy, the uterus is no bigger than an orange, but after pregnancy it EXPANDS. 

3.9a

3.9 recall the structure and function of the male and female reproductive systems

Male reproductive organ

Bladder – store urine

Testis – process of meiosis à produce gametes called sperm cells

Epididymis – store sperm cells

Vas Deferens – carry sperm cells to penis during sexual stimulation,

tube pulses and contracts

Prostate – adds 20 – 30% to volume of semen, contain sugars

and it is alkaline à neutralise the acidic secretion in the vagina

Seminal vesicles – also produce sugar based secretion, alkaline, about 70% of semen

Urethra – join the left and right testes, takes semen down the penis, exit for urine

Penis – carry sperm cells into the vagina during sexual intercourse

3.12

3.12 understand how the developing embryo is protected by amniotic fluid

In the uterus space, there is the amniotic fluid, which protects the developing embryo. The protection comes from the fact that the fluid (largely water) cannot be compressed and it absorbs pressure. Any force applied to the uterus wall will be absorbed by the amniotic fluid and prevent damage to the child. An example of such pressure absorber is when you try to kick in the swimming pool. It is difficult to generate a lot of power doing that. 

3.11

3.11 describe the role of the placenta in the nutrition of the developing embryo

The child is in the uterus, which is an environment filled with amniotic fluid. The child cannot digest, breathe or adequately carry out excretion. In order to receive nutrients, the umbilical cord grows out of the embryo, forming a placenta. The child’s blood vessels spread out to form the placenta (not the mother’s blood). The placenta grows into the wall of the uterus. Glucose, amino acids and fats travel through the wall of the uterus into the child’s bloodstream. The placenta has a large surface area and a thin barrier between the mother’s blood and the child’s blood. Nutrients (glucose, amino acids, fats) are given from the mother while excretion (carbon dioxide and urea) are given back to the maternal blood.