Lecture #11—Evidence from Genetics II

In this lecture we sketch out some of the major genetic concepts that have been discovered since Mendel’s pioneering work. Most of these you will have learned previously but this time you need to recall and define them. We review:

1)Concept of Polygene Inheritance

2) Concept of Multiple Alleles

3)Concept ofPleiotropy

4)Concept of Chromosomes

5)Concept that Chromosome Numbers Vary Among Species

6)Concept that Chromosomes Come In Pairs

7)Concept that Mendel’s Factors (Genes) occur in a particular place on chromosomes= locus

8)Concept that Many Genes Exist on Each Chromosome

9)Concept that sex-linked traits exist. These are traits carried on the sex chromosomes

10)Concept of Linkage—genes on the same chromosome are linked together

11)Concept that Cell Division Occurs

  1. Mitosis is the way that eukaryotic cells produce more body cells.
  2. Meiosis is the way that sex cells (gametes; sperm & eggs) are formed in eukaryotes.

12)Concept of Crossover—where sister chromosomes swap pieces during meiosis and increase genetic variability.

13)Concept of Sex Determination in Humans

You need to be able to define and explain all of these concepts in addition to those below.

Terms/Concepts to Define:

Polygenetic Traits

Multiple Alleles

Marfan’s syndrome

Chromosome Theory of Inheritance

Chromosome

Chromatin

Karyotype

Diploid

Haploid

Polyploid

Autosomes

Sex Chromosomes

Homozygous Dominant

Homozygous Recessive

Heterozygous

Sex-linked Traits

Mitosis

Meiosis

Chromatid

Phases of Mitosis and Meiosis: Interphase, Prophase, Metaphase, Anaphase, Telophase.

Crossover

Genetic Recombination

SRY Region of the Y Chromosome

Can you answer these questions?

1)Human intelligence is considered to be a polygene trait. What is meant be this and why do we believe this to be the case?

2)Suppose there is monogenetic trait that has 4 possible alleles, how many genotypes are possible?

3)Why can’t we see chromosomes during Interphase of the cell cycle?

4)Why might a cell with 27 chromosomes have trouble during meiosis?

5)Some human liver cells are polyploid. What might be a reasonable chromosome number for such a cell?

6)It is said that males who develop pattern baldness have received the trait from their mothers. Explain how this happens.

7)Mendel’s Law of Independent Assortment is incorrect. Explain what didn’t he know that made him so wrong?

8)List the major steps in mitosis and indicate what is happening in the cell at this stage.

9)List the major steps in meiosis and indicate what is happening in the cells at this stage.