1 / 11

Chapter Three:

Chapter Three:. Heredity and Environment. PowerPoints prepared by Cathie Robertson, Grossmont College. The Beginnings of Human Life. Development starts at the time of conception. During conception, the reproductive cells are fused together. Gametes: Sperm and ovum

ivy
Download Presentation

Chapter Three:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter Three: Heredity and Environment PowerPoints prepared by Cathie Robertson, Grossmont College

  2. The Beginnings of Human Life • Development starts at the time of conception. • During conception, the reproductive cells are fused together. • Gametes: Sperm and ovum • The fused cell is called the zygote.

  3. Zygote and Genotype • Gametes are haploid structures which combine to form a diploid zygote • Each cell (except gamates) has 23 pairs of chromosomes. • Chromosomes are double-helical or spiral structures with two strands. • Each strand has genes from one parent that pairs up with same genes on the second strand from another parent.

  4. Genes carry instructions to make all the proteins that guide development. • Genes: are the basic unit for the transmission of heredity instructions. • Every gene is a separate section on the chromosome and each contains instructions for a specific protein. • Genes are made up of DNAs (deoxyribonucleic acid).

  5. DNAs consist of the following four chemicals: adenine (A), thiamin (T), guanine (G) & cytosine (C) • DNA contains the instructions for building proteins that control the structure and function of all the cells that make up the body. • Four types of pairings are possible: A-T, T-A, C-G, and G-C. • A sequence of three pairings constitutes a gene.

  6. Sex Determination & Sex Ratio • In 22 of 23 pairs, the two chromosomes are very closely matched but not identical • some genes come in slight, normal variations called alleles • E.g. hair color: black and brown; eye-color: blue and brown, skin color: black, brown and white. • The 23rd pair is different • in females, it is designated XX • in males, it is designated XY

  7. Sex Determination and Sex Ratio, cont. • Females always contribute one X • Males will have 1/2 of the sperm contributing an X and the other half contributing a Y • The chances of having a male or a female are 50:50.

  8. Gene Expressions & Interactions • Most genetic traits are multifactorial • Environment and other genes (polygenic) • Some genes control and regulate the functioning of other genes • Additive genes: every gene contributes equally to the genetic expression (like height). • Dominant recessive genes

More Related