1. Genetics Unit Review

2. Introduction to Genetics

3. Genetics
Genetics - the scientific study of heredity. Heredity - Passing of traits from parents to offspring
Gregor Mendel was an Austrian monk. His work was important to the understanding of heredity.

4. Alleles and Genes
Gene - section of DNA which encodes for a protein that determines a physical trait ( ie eye color).
Allele - a version of a gene. Each gene can have multiple versions, or alleles.

5. Alleles Homozygous - two alleles are identical (BB, bb)
Heterozygous - two alleles are different (Bb)

6. Trait - a specific characteristic that varies from one individual to another.

7. Some alleles are dominant (Capital letter) and others are recessive (lower case letter).
An organism will always exhibit the dominant trait when present.

8. Genotype vs Phenotype
Phenotype - physical appearance of an inherited trait.
Genotype - genetic makeup of a person.

9. Relationship Between Genotype and Phenotype
The genotype codes for the phenotype.

10. Genetics and Probability
Probability - the likelihood that a particular event will occur.
The principles of probability can be used to predict the outcomes of genetic crosses.
PUNNETT SQUARES!

11. Punnett Squares
Punnett squares can be used to predict and compare the genetic variations that will result from a cross.
Capital letter (G) = dominant allele for green
Lowercase letter (g) = recessive allele for yellow
The dominant allele will mask the recessive allele

12. Punnett Square Example
Freckles (F) = Dominant
No freckles (f) = Recessive
F f f Ff ff
Ff - Heterozygous
ff - Homozygous
FF - Homozygous Ff ff
Ff - Freckles
ff - No freckles
FF - Freckles
50% freckles
50% no freckles

13. Meiosis and Sexual Reproduction

14. Meiosis Making Sperm and Eggs
Meiosis occurs in sexual reproduction when a diploid (2n) germ cell produces 4 haploid (1n) daughter cells that can mature to become gametes (sperm or egg)

15. Goal #1 of Meiosis Goal: Reduce genetic material by 1/2.
from mom
from dad
child
meiosis reduces
genetic content
too
much!
Just right!
Why? 1n (Mom) + 1n (Dad) = 2n (offspring)

16. Goal #2 of Meiosis
Crossing over occurs during Prophase I when parts of homologous chromosomes overlap. Crossing over increases genetic variation.

17. Comparison of Mitosis and Meiosis
# of divisions 1 2
# of daughter cells 4
Genetically identical
yes no
Chromosome #
Same as parent
Half of parent
Where
Somatic cells
Sex cells
When
Throughout life
At sexual maturity
Role
Growth and repair
Sexual reproduction

18. 2 Phases of Meiosis Meiosis I - Homologous chromosomes separate
Meiosis II - sister chromatids separate

19. Phases of Meiosis X X Y Y X

20. Location of Meiosis X X Y Y X
Males - Testes Females - Ovaries

21. Meiosis in Males and FemalesX X Y Y X

22. Diploid (2n) vs. Haploid (1n)
Diploid - Cells with 2 copies of each chromosome.
In humans, all cells except sex cells (gametes)
Haploid - Cells with only 1 copy of each chromosome.
In humans, only sex cells (gametes)

23. Chromatids vs. Homologous Chromosomes
Sister chromatids are 2 duplicates of a chromosome made during DNA replication.
Homologous chromosomes are a pair of the same chromosome, one from Mom, one from Dad.
Homologous
chromosomes

24. Crossing Over
Crossing over occurs during Prophase I when parts of homologous chromosomes overlap. Crossing over increases genetic variation.

25. Goal #1 of Meiosis Goal: Reduce genetic material by 1/2.
8 chromosomes at the beginning of meiosis.
4 chromosomes at the end of meiosis.

26. The Structure of DNA

27. Nucleotide Phosphate Nitrogenous Base Deoxyribose Sugar
One deoxyribose sugar, one phosphate and one nitrogenous base make a nucleotide.

28. Nitrogenous Bases Purines: Adenine (A) Guanine (G) Pyrimidines:
Cytosine (C)
Thymine (T)
Purines are double ring bases and Pyrimidines are single ring bases

29. Hydrogen Bonds Two strands of DNA are held together by hydrogen bonds
RNA only has one strand. No hydrogen bonds

30. Base Pairing Rule
Guanine Cytosine Adenine Thymine

31. Structure of DNA Sides of ladder = sugars (S) and phosphates (P)
Rungs of ladder = nitrogenous base (A,T,G,C)

32. The Shape of the DNA Molecule
DNA is a very long polymer
The basic shape is like a twisted ladder
This is called a double helix
The DNA double helix has two strands twisted together

33. Components of DNA Nucleotide - C Deoxyribose sugar - E
All nitrogenous bases - A, B, D, F
Phosphate - G
Hydrogen bond - H

34. Structure of DNA
The backbone of DNA is repeating phosphates and deoxyribose sugar
The rungs are nitrogenase bases

35. Central Dogma DNA Transcription RNA Translation Protein (Nucleus)
(Cytoplasm)
DNA Transcription RNA Translation Protein

36. DNA Replication DNA Replication occurs in the nucleus.
Two strands of DNA identical to the parent DNA are produced.
DNA has to be copied before the cell divides.

37. DNA Transcription DNA Transcription occurs in the nucleus.
Messenger RNA (mRNA) is produced.
mRNA carries copies of the instructions for making proteins from the nucleus to the ribosome.

38. DNA Translation DNA Translation occurs in the cytoplasm.
Amino acids are produced.
Conversion of mRNA into an amino acid sequence that makes protein.

39. Central Dogma DNA Transcription RNA Translation Protein (Nucleus)
(Cytoplasm)
DNA Transcription RNA Translation Protein

40. Semi-Conservative Replication
Parent DNA
Strand
DNA
Replication
Two identical Daughter
DNA Strands
Replication - DNA to DNA

41. DNA Replication DNA molecule untwists and unzips into two strands
Free nucleotides attach and 2 new strands are produced using the old strand as a template
DNA replication is semi-conservative: one DNA strand is conserved, other is new

42. Replication Bubbles
In eukaryotes, DNA replication occurs at hundreds of sites. Replication proceeds in both directions until each chromosome is completely copied. The sites where replication occurs are called replication forks.

43. Replication Fork DNA replication begins at the Origins of Replication
Two strands open forming Replication Forks
New strands grow at the forks

44. DNA Replication Parent strands - D & E New strands - A & B
Enzyme at C - DNA Polymerase

45. RNA vs DNA RNA DNA single stranded short ( 1 gene) ribose sugar
uracil (U)
double stranded
long (many genes)
deoxyribose sugar
thymine (T)
Sugar
Phosphate
Backbone
Nitrogenous
Base
Nitrogenous
Base
Sugar
Phosphate
Backbone

46. Protein Synthesis Requires Three Types of RNA
mRNA -
Messenger
RNA
2. tRNA - Transfer RNA
3. rRNA - Ribosomal RNA

47. DNA Transcription
mRNA is formed from DNA in the nucleus by a process called DNA transcription
mRNA goes from the nucleus to the ribosome in the cytoplasm
mRNA is translated into amino acids to make a protein

48. Parts of Transcription/Translation
A - DNA E - Codon K - mRNA
B - DNA template F,G,H - tRNA L - Amino acid chain
C - mRNA I - Anticodon M - Amino acid
D - Nuclear Memb. J - Ribosome

49. Central Dogma Summary

50. Translation of mRNA into Amino Acids
The “words” of the DNA “language” are triplets of bases called CODONS
3 bases = 1 triplet = 1 codon - located on mRNA

51. Transfer RNA (tRNA) codon
anticodon
The anticodon is complementary to the 3 bases of the codon on the mRNA molecule.

52. Practice A T C G A C T T A G C T G A A T C G A C T U A G C U G A
Original DNA
Replication
Comp. DNA
T A G C T G A
A T C G A C T
Original DNA
Transcription
mRNA
U A G C U G A

53. Mutations TAC GCC AGC CCG Original TAC CCA GCC CG
Deletion
Mutation 2
TAC GCC AGC CCG Original
TAA CGC CAG CCC G
Insertion

54. Mutations TAC GCC AGC CCG Original TAC GCC TGC CCG Substitution
Which mutations are frameshift mutations?
Deletion and Insertion