GENETICS I CHROMOSOMES GENETICS I CHROMOSOMES

A. CHROMOSOMES Chromosomes are found in the nucleus of the cell Chromosomes are found in the nucleus of the cell

CHROMOSOMES CHROMOSOMES CHROMOSOMES within a cell are arranged in pairs from the largest to the smallest, followed by sex- chromosomes CHROMOSOMES within a cell are arranged in pairs from the largest to the smallest, followed by sex- chromosomes

–As you can see, we have: two #1 chromosomes, two # 2 chromosomes, two # 3 chromosomes, and so on for all the pairs. –As you can see, we have: two #1 chromosomes, two # 2 chromosomes, two # 3 chromosomes, and so on for all the pairs.

B. AUTOSOMES The first 22 pairs are called AUTOSOMES, and are shared by both the male and the female. The first 22 pairs are called AUTOSOMES, and are shared by both the male and the female.

C. SEX CHROMOSOMES C. SEX CHROMOSOMES Chromosomes in pair #23 are called sex- chromosomes. Chromosomes in pair #23 are called sex- chromosomes.

FEMALES –A woman has two X sex- chromosomes XX XX

MALES MALES A man has one X sex-chromosome and one Y sex- chromosome. A man has one X sex-chromosome and one Y sex- chromosome. XY XY

D. KARYOTYPES WHAT’S A KARYOTYPE?

Karyotype Karyotype A karyotype is a photograph of chromosomes grouped in order in pairs. A karyotype is a photograph of chromosomes grouped in order in pairs. Karyotyping is a test to examine chromosomes in a cell, which can help identify genetic problems as the cause of a disorder or disease. Karyotyping is a test to examine chromosomes in a cell, which can help identify genetic problems as the cause of a disorder or disease. This test can Count the number of Chromosomes Count the number of Chromosomes Look for structural changes in the chromosomes Look for structural changes in the chromosomes

SINGLE CHROMOSOME KARYOTYPE

PAIRED CHROMOSOMES KARYOTYPE

Karyotypes of a male and female Karyotypes of a male and female

F. Determining sex

A. FERTILIZATION A. FERTILIZATION Life begins when a spermatozoa and an ovum unite to form one single cell called a zygote, which as of that moment, will undergo a series of divisions (mitosis) that will result in the birth of an infant. Life begins when a spermatozoa and an ovum unite to form one single cell called a zygote, which as of that moment, will undergo a series of divisions (mitosis) that will result in the birth of an infant. This process is known as fertilization, and it takes place in the female's uterine tubes. This process is known as fertilization, and it takes place in the female's uterine tubes.

Humans have 23 pairs of chromosomes Humans have 23 pairs of chromosomes 1-22 are homologous and are called autosomes 1-22 are homologous and are called autosomes Pair 23 are the sex chromosomes and determine your sex Pair 23 are the sex chromosomes and determine your sex

Fertilization happens when an egg cell and sperm unite Note: Egg and sperm not shown to scale Most of our cells contain 46

What determines if you are a male or female? What determines if you are a male or female? XY = male XY = male XX = female XX = female Human Female Karyotype

As a result of chromosome separation during meiosis, each gamete contains one sex chromosome and one of each pair 1-22 As a result of chromosome separation during meiosis, each gamete contains one sex chromosome and one of each pair 1-22

F. GAMETES (SEX CELLS) F. GAMETES (SEX CELLS) All egg cells contain 1 X chromosome All egg cells contain 1 X chromosome 50% of sperm cells contain an X chromosome 50% of sperm cells contain an X chromosome The other 50% contain a Y chromosome The other 50% contain a Y chromosome So, what determines the sex of the zygote? So, what determines the sex of the zygote?

What about twins? Identical twins come from one fertilized egg that splits early in the pregnancy and develops into more than one fetus. This is different because not only do the fetuses share the same placenta, but they also share the same genetic material. That is why they are identical (they have the same hair color, eye color, sex, and blood type). Identical twins come from one fertilized egg that splits early in the pregnancy and develops into more than one fetus. This is different because not only do the fetuses share the same placenta, but they also share the same genetic material. That is why they are identical (they have the same hair color, eye color, sex, and blood type).