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11.9Chapter 11: Human Genetics and Development

Chapter 11 Review: Human Genetics and Development — Alhussan Biology - Stage 9 Revision Notes & Topical Questions

5 min read 6 parts Lesson 9 of 9 1 quiz

📚 Alhussan Biology - Stage 9 Hub / Topical Revision
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Lesson summary

11.9 Chapter 11 Review: Human Genetics and Development — Alhussan International Academy — Biology (Stages 7–9) notes: Revise reproduction, fertilisation, inheritance, fetal development and the effects of maternal lifestyle from Chapter 11.Gametes — testes make sperm and ovaries m…

  • Amniotic fluid
  • Umbilical cord
  • Harmful substances
  • Premature babies
  • Breast milk
  • Antenatal care

Part 1 of 4Reproduction and fertilisation

Gametes
  • Gametes testes make sperm and ovaries make eggs, each with 23 chromosomes.
  • Sperm have tails and mitochondria and carry enzymes in the head.
  • Eggs are large with a food store.
Fertilisation
  • Fertilisation it occurs in the oviduct when a sperm nucleus fuses with an egg nucleus to form a zygote with 46 chromosomes.
  • Many thousands of sperm swim towards the egg, and the nucleus of only the successful sperm fuses with the egg nucleus.
Embryo
  • Embryo the zygote divides by mitosis, and the embryo implants in the uterus lining about a week later.

Part 2 of 4Genes and inheritance

DNA
  • DNA chromosomes are long molecules of DNA, and genes are short sections that code for proteins.
Alleles
  • Alleles different versions of a gene.
  • Offspring inherit one allele of each gene from each parent, so they show variation.
Sex
  • Sex females are XX and males XY, and the sperm decides the sex, with equal chances of a boy or girl.
Variation
  • Variation it comes from both genes and the environment.
  • Identical twins have the same earlobe shape and blood group because these are genetic.
  • Differences in height and body mass between identical twins are due to different environments, such as diet and exercise.

Part 3 of 4Development and birth

1Amniotic fluid
  • Amniotic fluid it cushions the fetus and keeps the temperature steady.
2Placenta
  • Placenta it exchanges oxygen, nutrients, carbon dioxide and urea by diffusion without mixing blood.
3Umbilical cord
  • Umbilical cord it carries blood between fetus and placenta.
4Birth
  • Birth labour begins with contractions of the uterus, the baby is born and the placenta follows.

Part 4 of 4Health of mother and baby

Nutrition
  • Nutrition folic acid, iron, calcium and protein, together with antenatal care, give the baby the best start.
Harmful substances
  • Harmful substances smoking, alcohol and some drugs harm the fetus.
  • Smoking reduces birth weight because carbon monoxide lowers oxygen supply.
  • Drugs can cross the placenta, so doctors take extra care choosing medicines for a pregnant woman.
Premature babies
  • Premature babies they are helped by incubators, ventilators, surfactant, feeding tubes and careful hygiene.
Breast milk
  • Breast milk it contains antibodies.

Key terms

TermMeaning
ZygoteThe cell formed when a sperm and an egg nucleus fuse.
AlleleA version of a gene.
PlacentaThe organ that exchanges materials between mother and fetus.
GameteA sex cell with half the usual number of chromosomes.
Antenatal careRegular health checks during pregnancy.
SurfactantA liquid that stops the lungs sticking together.

Avoid these mistakes

1
Mixing up the oviduct, where fertilisation occurs, and the uterus.
2
Saying the Y chromosome comes from the mother.
3
Forgetting that the placenta provides oxygen and removes carbon dioxide.
4
Describing a gene and an allele as the same thing.

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