1. Lesson 2: Sexual Reproduction
Unit 5: Genetics
Lesson 2: Sexual Reproduction

2. Bell Work What does DNA stand for?
What is a chromosomes and what is found on a chromosome?
Due to the fact that we did not finish the lab, the note packet will be due on Tuesday by the end of the school day.

3. Today’s Objectives
Bell Work
Lesson 2 Notes
Review Questions

4. Standards & Objectives
Standard 7.L.4: The student will demonstrate an understanding of how genetic information is transferred from parent to offspring and how environmental factors and the use of technologies influence the transfer of genetic information.
7.L.4A. Conceptual Understanding: Inheritance is the key process causing similarities between parental organisms and their offspring. Organisms that reproduce sexually transfer genetic information (DNA) to their offspring. This transfer of genetic information through inheritance leads to greater similarity among individuals within a population than between populations. Technology allows humans to influence the transfer of genetic information. Performance Indicators: Students who demonstrate this understanding can:
7.L.4A.2 Construct explanations for how genetic information is transferred from parent to offspring in organisms that reproduce sexually.
It is essential that students construct explanations for how genetic information is transferred from parent to offspring in organisms that reproduce sexually.

5. There are two types of chromosomes: Autosomes and sex chromosomes
More than 1200 genes are on the human X chromosome.
The human Y chromosome contains only about 140 genes.

6. Autosomal Chromosomes
The other 22 pairs of non-sex chromosomes are called autosomal or autosomes.
Humans have 46 chromosomes
23 from the male parent
23 from the female parent
Each set of chromosomes is homologous
Each of the 23 chromosomes from the male parent will “match” with each of the 23 chromosomes from the female parent.

7. How many chromosomes
Organism
Body Cell (2n)
Sex Cells (n)
Fruit fly 8 4
Garden pea 14 7
Corn 20 10
Tomato 24 12
Leopard Frog 26 13
Apple 34 17
Human 46 23
Chimpanzee 48
Dog 78 39
Adder’s tongue fern
1260
630
Is there any correlation between organism size and number of chromosomes?
Do animals have more chromosomes than plants?

8. Sex Chromosome and Sex Determination
In humans gender is determined by the sex chromosomes.
The 23rd pair.
50% of sperm cells carry X, 50% carry Y.
100% of egg cells carry X.
XX = female and XY= male.
Which parent determines the gender of the baby?

10. Diploid vs. Haploid
Cells can have a full set of chromosomes (diploid), or half a set of chromosomes (haploid).
The diploid number is ALWAYS even.
Diploid Cells
Haploid Cells
 Represented by 2N
Represented by “N”.
 Cells that have both sets of homologous chromosomes.
 Cells only ONE copy of each chromosomes
 In humans the diploid number is 46 (2 times the haploid number)
In humans, the haploid number is 23.
N = 23
Found in body cells, called somatic cells.
 Found only in sex cells (egg and sperm)

11. Exit Slip What is the difference between haploid and diploid?
What are sex chromosomes?
What is a gene?