How many chromosomes do humans have?

1. STUDY! How many chromosomes do humans have? Do you remember what this is called? Humans have 46 chromosomes. They occur in 23 pairs! A karyotype

2. STUDY! Pair 1 – 22 are known as autosomes.

3. STUDY! The 23rd pair are called sex chromosomes. • X Chromosome • Y Chromosome Do you remember what combination codes for female and male? • XX – Female • XY – Male

4. Sex Linked Genes • Some genes are located on the X chromosome. • These traits are called sex-linked traits and are controlled by the genes on the x chromosome. • Females receive two alleles for these genes, but males only receive one, since they only get one X along with the Y. • Because XX = Female and XY = Male • Examples include color blindness, pattern baldness and hemophilia. STUDY!

5. Colorblindness • Females who are heterozygous for a trait are known as carriers • A female can be • XBXB – normal • XBXb –carrier • XbXb - colorblind • Males CANNOT be carriers because they only have one X chromosome • A male can be • XBY – Normal • XbY - colorblind STUDY! This PS shows a cross between a normal man and a woman who is a carrier. (Notice that NO allele is attached to the Y!)

6. Sex-linked Problem… • A woman has normal color vision and is married to a man with normal color vision. One of their two sons has normal color vision but the other son is colorblind. How was this possible? • First, figure out the genotypes of the parents. Mom = XBXb because she has to be carrier Dad = XBY because we know he is normal • Will any of their daughters be colorblind? Will any of their daughters be carriers? • Do the Punnett square to find out!! STUDY!

7. STUDY! A pedigree is used to show genetic inheritance within a family • Squares represent Males • Circles represent Females • Horizontal lines show marriages • Vertical lines show offspring • So, let’s analyze this pedigree!

9. A pedigree is a graphic representation of genetic inheritance. • In most instances, the shapes are either shaded or not. • If the shape is shaded, then the individual has the particular trait. STUDY!

10. Celebration of Learning Moment!  Pedigree Problem Worksheet

11. Occasionally, problems occur at the chromosomal level.

12. We call these problems genetic disorders • A genetic disorder is a disease that is caused by an abnormality in an individual's DNA. • Abnormalities can range from a small mutation in a single gene to the addition or subtraction of an entire chromosome or set of chromosomes. • There are various genetic disorders, some dominant, recessive, sex-linked, co-dominant.

13. We’ll discuss the more frequently encountered genetic problems human have. WARNING: Some images may be explicit or hard to see. Use your knowledge of these disorders to be kind and compassionate to others!

14. Dominant Allele Disorders • What does it mean by dominant? • Dominant dominates over the recessive allele. • DD or Dd Examples: • Achondroplasia • Huntington's Disease

15. Achondroplasia • Long bones do not develop properly • Results in unusually short arms and legs, a large head and relatively long torso • Only 1/8th of the children born with this condition inherited it from a parent. • Most cases of achondroplasia occur spontaneously and are the result of a new mutation in an egg or sperm of one of the normal- appearing parents. 

16. Huntington's Disease • Progressive, degenerative disease • Causes certain nerve cells in your brain to waste away • Results in uncontrolled movements, emotional disturbances and mental deterioration. • Huntington's disease is inherited as a dominant allele so if one parent has this disease, the offspring have a 50% chance of inheriting it.

17. Recessive Allele Disorders • What does it mean to be recessive? • Dominated by dominant allele • What HAS to be present to have a recessive phenotype? • BOTH recessive alleles Examples: • Cystic Fibrosis • Tay – Sachs Disease • Albinism

18. Cystic Fibrosis • Inherited recessive disorder resulting from a mutation of the gene that regulates the secretory glands, including mucus and sweat glands. • The characteristics of cystic fibrosis are salty tasting skin, normal appetite but poor growth and poor weight gain, excess mucus production, frequent chest infections and coughing/shortness of breath. • Both parents must carry the allele for the child to inherit the condition. 

19. Tay-Sachs Disease • Fatal genetic lipid storage disorder in which harmful quantities of a fatty substance build up in tissues and nerve cells in the brain. • Infants with Tay-Sachs disease appear to develop normally for the first few months but as fatty material builds up, a relentless deterioration of mental and physical abilities occurs. • The child becomes blind, deaf, and unable to swallow. Muscles atrophy and they can no longer swallow. • Children with Tay-Sachs disease usually die by age 4. • Both parents must carry the allele for a child to inherit the condition

20. Albinism • Recessive disorder that occurs when one of several genetic defects makes the body unable to produce or distribute melanin, a natural substance that gives color to your hair, skin, and iris of the eye. • In one type of albinism, people have white or pink hair, skin, and iris color, as well as vision problems. • Another type of albinism, called ocular albinism type 1 affects only the eyes. The person's skin and eye colors are usually in the normal range. However, an eye exam will show that there is no coloring in the back of the eye .

21. Can you remember any of the genetic disorders we’ve previously discussed? • Klinefelter’s Syndrome: Males with one extra X chromosome (XXY) • Turner Syndrome: Female disorder where girl only has only fully functional X chromosome • Down Syndrome: Trisomy of the 21 chromosome • Sickle Cell Anemia: Misshaped red blood cells

22. Create an informative poster! • You and your partner will pick a genetic disorder and research it • Create a detailed AND creative poster to inform others about your chosen disorder. • This is the ONLY time you will be allowed to use your device. And, you should ONLY be researching!!!