1. Human Karyotypes and Heredity
Notes #22 & #23
I can:
Identify male or female based on looking at a person’s karyotype
Identify abnormalities within a karyotype
Identify how traits are passed from parent to offspring

2. Why must scientists observe a cell’s genetic material during mitosis?
Scientists can visualize the chromosomes in a cell by photographing them while they are condensed in mitosis.
Why must scientists observe a cell’s genetic material during mitosis?

3. A picture of chromosomes arranged in sets and according to size is called a karyotype.
Human karyotype
Humans have 2 sets of 23 chromosomes (46 in total).
each pair of chromosomes is homologous – they are the same size and contain the same genetic information

4. 23 Half (23) of your chromosomes come from your father…
from mom
from dad 23
…and half (23) come from your mother.
The fertilized egg, or zygote, has all 46 chromosomes necessary for life.

5. A picture of chromosomes arranged in sets and according to size is called a karyotype.
Human karyotype
The 23rd pair of chromosomes are sex chromosomes. They determine the sex of the individual.
females: XX
males: XY

6. Sex chromosomes X chromosome Y chromosome
The Y chromosome contains very few genes of importance, other than the SRY gene, which determines maleness.

7. A picture of chromosomes arranged in sets and according to size is called a karyotype.
Human karyotype
The remaining 22 pairs are called autosomes.

8. Dog karyotype

9. Mouse karyotype

10. T-P-S
Does the size of the genome (how many chromosomes there are) correlate with the complexity of the organism?

11. XX XY Y X All human eggs carry an X chromosome.
after one round of meiosis…
All human eggs carry an X chromosome.
Sperm can contain an X or Y chromosome. XX XY
There is a 50% chance that the zygote produced from the fertilized egg is female (XX), and there is a 50% chance that it is male (XY).

12. What sex is this individual?
Karyotypes can tell us two important things: the sex of an individual, and whether there is a genetic disorder.
What sex is this individual?

13. What sex is this individual?
Karyotypes can tell us two important things: the sex of an individual, and whether there is a genetic disorder.
What sex is this individual?

14. What’s wrong with this individual?
If nondisjunction occurs during the formation of gametes, abnormal numbers of chromosomes result
Down Syndrome is the result of trisomy 21, or 3 copies of chromosome 21.

15. What’s wrong with this individual?
Klinefelter’s Syndrome (XXY)

16. What’s wrong with this individual?
Turner Syndrome (XO)

17. Intro to Heredity

18. Why do children usually look like their parents?

19. Why do children usually look like their parents?

20. Why do children usually look like their parents?

21. Genetics is the study of heredity, how traits are passed on to offspring.
A trait is a characteristic that varies from one individual to another.
eye color
height
limb length
ability to carry a tune
risk of developing breast cancer
number of fingers
length of legs proportional to body
sickle cell trait

22. Gregor Mendel
( )
The principles Gregor Mendel derived from his study of peas are still used in genetics to this day.

23. A gene is a sequence of DNA that codes for a trait.
PRINCIPLE #1
Biological inheritance is determined by factors called genes that are passed from one generation to the next.
A gene is a sequence of DNA that codes for a trait.
An allele is a version or form of a gene.
= gene for eye color
= allele for brown eyes
= allele for blue eyes

24. Some alleles are dominant and others are recessive.
PRINCIPLE #2
Some alleles are dominant and others are recessive.
An organism with a dominant allele will always show that form of the trait. Represented by capital letter.
A recessive allele is only expressed when the dominant allele is not present. Represented by lowercase letter.
purple
white

25. ? BB black B = black b = white Which one is dominant?
Which one is recessive? ? BB
black

26. ? Bb black B = black b = white Which one is dominant?
Which one is recessive? ? Bb
black

27. ? bb white B = black b = white Which one is dominant?
Which one is recessive? ? bb
white

28. ? Bb brown B = brown b = blue Which one is dominant?
Which one is recessive? ? Bb
brown

29. ? bb blue B = brown b = blue Which one is dominant?
Which one is recessive? ? bb
blue

30. ? BB brown B = brown b = blue Which one is dominant?
Which one is recessive? ? BB
brown

31. ? pp white P = purple p = white Which one is dominant?
Which one is recessive? ? pp
white

32. ? Pp purple P = purple p = white Which one is dominant?
Which one is recessive? ? Pp
purple

33. ? PP purple P = purple p = white Which one is dominant?
Which one is recessive? ? PP
purple

34. Because you inherit one copy of each gene (allele) from each parent, you have two alleles of each gene. The combination of alleles in an individual is represented by using the same letter to describe the trait.
= b
= B bb Bb BB

35. Genotype
An organism’s genotype is its genetic makeup, or combination of alleles.
genotype = bb

36. Phenotype phenotype = blue eyes
An organism’s phenotype is its physical characteristics.
phenotype = blue eyes

37. Which are heterozygous?
Describing Genotypes
homozygous – two of the same allele for a single trait
heterozygous – two different alleles for the same trait
Which are homozygous?
Which are heterozygous? bb Bb BB
homozygous dominant
homozygous recessive
heterozygous