Unit 4: Genetics

B-4.3 Explain how DNA functions as the code of life and the blueprint for proteins.

Key Concepts

n  Sex chromosomes vs. Autosomes

n  Gametes vs. Body Cells

n  Haploid vs. Diploid

What You Already Know… In the 7th grade, you summarized how genetic information is passed from parents to offspring using the terms genes, chromosomes, inherited traits, genotype, phenotype, dominant traits, and recessive traits.

It is Essential For You to Know…

n  DNA is considered the “code of life” (genetic code) because it contains the code for each protein that the organism needs.

n  Each cell in an organism’s body contains a complete set of chromosomes (diploid) except for gametes, which only contain half of the complete set (haploid)

n  Each chromosome consists of hundreds of genes.

OBJECTIVES n  Explain how DNA functions as the code

of life and the blueprint for proteins. n  n  Compare autosomes and sex

chromosomes.

n  Differentiate between body cells and gametes.

n  Compare haploid cells and diploid cells.

Vocabulary

1.  Somatic Cell 2.  Gamete 3.  Homologous chromosome 4.  Autosome 5.  Sex chromosome 6.  Diploid 7.  Haploid

Karyotype

The picture to the left shows all the chromosomes in a human. It is called a karyotype.

Chromosomes There are two types of chromosomes:

autosomes and sex chromosomes

Remember… n  Humans have 46 chromosomes

n  23 from the male parent n  23 from the female parent

n  Each set of chromosomes is homologous n  Each of the 23 chromosomes from the male

parent will “match” with each of the 23 chromosomes from the female parent. n  They are homologous chromosomes.

This a picture of homologous chromosomes because…..

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 24

Dog 78 39

Adder’s tongue fern 1260 630

How many Chromosomes do Organisms Have?

Is there any correlation between organism size and number of chromosomes?

Do animals have more chromosomes than plants?

Is the diploid number always an even number?

Sex Chromosomes & Sex Determination

n  In humans gender is determined by the sex chromosomes.

n  Non-homologous, 23rd pair. n  50% of sperm cells carry X, 50% carry Y. n  100% of egg cells carry X. n  If the 23rd pair of chromosomes

is XX…female, if XY…male. n  Which parent determines

the gender of the baby?

Remember….

n  Diploid n  Cell that has both sets

of homologous chromosomes.

n  2N n  In humans, the diploid

number is 46 n  2N = 46, a full set

n  Found in body cells (called somatic cells)

n  Mitosis

Remember….

n  Haploid n  A cell that has only 1

set of chromosomes. n  N n  In humans, the haploid

number is 23 n  N = 23, half of the full

set

n  Found in gamete cells (egg and sperm)

n  Meiosis

Meiosis