3.19b F1 x F1 Cross

3.19 describe patterns of monohybrid inheritance using genetic diagrams

P₁:                    Red petal x White Petal
F₁:                    Red (Rr)
F₁Cross (F₁ x F₁)
Phenotype:                    Red Petal x Red Petal
Genotype:                      Rr x Rr
Meiosis:                          R or r x R or r

Random Fertilisation:

	Female
Male		R	r
	R	RR	Rr
	r	Rr	Rr

Genotype F₂:                    RR : 2Rr : rr

Phenotype:                        Red : 2Red : White
Monohybrid F₂ Ratio:                    3:1

3.19a P1 x P1 Cross

3.19 describe patterns of monohybrid inheritance using genetic diagrams

3.18b Codominance

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

3.18 Phenotypes and Genotypes

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

3.2 Fertalisation

3.2 understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo

1. The Adult male and female Gametes are formed by Meiosis
2. These Gametes have half the number of chromosomes as a diploid cell
3. The two opposite gametes fuse to form a zygote, this is now a diploid cell containing a full set of chromosomes
4. The Zygote goes the mitosis to divide into a ball of cells, known as a blastula which then grows to form the embryo.

I have created the diagram below to try to visually explain the concept.

3.9 Reproductive Organs

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

The Male Reproductive Organ System

There are 8 organs that make up the male reproductive system these are:

1. Bladder – Stores urine
2. Testis – Carries out meiosis which produces the male gamete; the sperm cell
3. Epididymis – Store sperm cells
4. Vas deferens – carries sperm cells to the Penis
5. Prostate – 20/30% of the volume of the semen, contains sugars. (Alkaline solution, to neutralise the acidic secretions within the vagina)
6. Seminal Vesicles – Produces 70% of the volume of semen (also sugar based and alkaline)
7. Urethra – common tube that joins the left and right vas deferens, transports semen and urine down the penis
8. Penis – carry sperm cells into the vagina during sexual intercourse

Note: Semen = Sperm Cells + Prostate secretions + Seminal Vesicles secretions

The Female Reproductive Organ System

There are 7 organs in the female reproductive system:

1. Ovary – Meiosis occurs to form the female Gamete; the egg cell
2. Oviduct – Carry the eggs to the uterus, Fertilisation occurs here. (a.k.a. the fallopian tubes)
3. Uterus wall – the wall of the uterus, made of muscle, stretches to accommodate a pregnancy
4. Uterus lining – accepts and develops the egg into a embryo and then to a child, the placenta implants into here.
5. Uterus Space – where the embryo develops to an unborn child
6. Cervix – Entrance to the uterus,
7. Vagina – Collects the sperm cells from the penis and allows them to pass through the cervix into the uterus.

Note: Before pregnancy the entire uterus structure is no larger than an orange

3.12 Amniotic Fluid

3.12 Understand how the developing embryo is protected by amniotic fluid.

Surrounding the developing embryo is a fluid, the amniotic fluid.
This fluid can protect the embryo as it acts as a “shock absorber”; the fluid is mainly water and so cannot be compressed so it absorbs all external pressures to the uterus preventing damage to the embryo.
Furthermore thee embryo “floats” in the amniotic fluid so there is no pressure applied onto the developing bones and muscles of the unborn child mean that it can grow and develop much easier.

3.11 Placenta

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

The developing embryo can’t digest, breathe or excrete so it needs a way to receive nutrients from the mother in order to grow, obviously it gets these nutrients from the mother through what is called the Placenta

The Placental structure consists of the Umbilical Cord containing blood vessels that lead from the embryo to the placenta. It is important to know that the placenta grows out from the embryo not from the mother. Initially the umbilical cord grows up towards the walls of the uterus and upon contact the child’s blood vessels spread out to form the placenta inside the walls of the uterus.

Glucose, amino acids and fats travel through the maternal blood vessel and cross into the embryo’s blood through the placenta. CO₂ and Urea from the embryo travel up the umbilical cord and cross into the mother’s blood also at the placenta. To make this process efficient the placenta has a large surface area and the barrier between the mother’s and child’s blood is very thin.