1. 3.3 Review PBS

2. How is DNA passed to new cells during cell division?
Mitosis
Makes two duplicate body cells
Used for growth and repair of cuts
Before the cell divides the DNA in the chromosomes will replicate so each cell has the same DNA and same amount of chromosomes

3. How is DNA passed to new cells during cell division?
Meiosis
Makes 4 different sex cells (gametes)
Used to divide chromosome number in half so sex cells can combine during fertilization and produce a zygote with the same amount of chromosomes as the parent.
Similar process as mitosis, but cells divide twice after DNA replicates to produce 4 cells with half as many chromosomes.

4. What is a chromosome?
Structures in the nucleus that are composed of the DNA wrapped around a protein
Humans have 46 chromosomes in their body cells (only 23 in sex cells)
There are 22 pairs of homologous chromosomes (chromosomes that contain the same alleles in the same location)
Alleles – are one type of a gene. There are dominant and recessive alleles.

5. What is a chromosome? Karyotype 46 chromosomes
44 or them or 22 pairs are autosomal chromosomes, which do not affect your gender
2 or 1 pair are sex chromosomes, which determine gender
XX is a female
XY is a male
Karyotype
Picture of all the chromosomes in a cell
male
female

6. How are traits passed through the generations?
Parents pass on their genes to their offspring.
The genotype (genes) that child receives determines their phenotype (appearance)
If a dominant allele is present then the person will have the dominant phenotype
If only recessive alleles are present then the person will have the recessive phenotype
Some individuals can be carriers (Bb) and pass on the recessive allele even though they have the dominant phenotype