1. Life Science
Chapters 4 Genetics

2. Gregor Mendel “father of genetics”
experiments crossing pea plant traits
a. Tall or short plants
b. Round or wrinkled peas
c. Yellow or green peas
d. Smooth or pinched pods
e. Green or yellow pod color

3. New Terms Gene: factor that controls a trait
Allele: the different forms of a gene
Purebred: always produces the same trait
Hybrid: an organism w/ two different alleles for a trait – it is heterozygous
Heredity: the passing of traits from parents to offspring
Genetics: the scientific study of heredity

4. More Terms…
Dominant allele: trait shows up in the organism when the allele is present, represented by a Capital letter ie “T” for tall
Recessive allele: trait is masked or covered up, represented by a small case letter ie “t” for short

5. More Terms…
Probability: A number that describes how likely an event will occur
Punnett square: a chart that shows all possible combinations of alleles
Phenotype: The outward visible trait being shown
Genotype: The genetic makeup of the trait
Homozygous: both alleles are the same for the trait in question
Heterozygous: Alleles are different for the trait in questions

6. Punnett Square
Way of predicting the possible phenotype & genotype outcomes when parents are crossed
Must be able to determine the genotypes of the parents Bb Bb Bb Bb

7. Punnett Square
Way of predicting the possible phenotype & genotype outcomes when parents are crossed
Must be able to determine the genotypes of the parents
In this case, when two hybrids are crossed, the possible outcomes are:
the phenotype ratio is 3:1
3 dominant
1 Recessive
genotype ratio is 1:2:1
1 Homozygus dominant
2 Heterozygus
1 Homozygus recessive

9. Reminder… Phenotype: The outward visible trait being shown
Genotype: The genetic makeup of the trait
Homozygous: both alleles are the same for the trait in question
Heterozygous: Alleles are different for the trait in questions

10. Codominance: When both alleles are expressed in offspring
Example: A white feathered chicken and a black feathered chicken make a black and white feathered chicken (both alleles are dominant)
Anna’s Eyes???? 

11. Meiosis
Meiosis is the process by which the number of chromosomes is reduced by h____ to form sex cells – spe___ and eggs.
alf rm

12. Meiosis
Meiosis I
Meiosis II

13. Gamete (Sex Cell) Formation
Normal chromosome # 23 pairs = 46 total
Diploid – a cell that has both homologus chromosomes ( one from each parent) –2N
Haploid – 1N - has only one of the homologus chromosomes (one from the father or the one from the mother)
Egg & Sperm cells are haploid so when they combine during fertilization the zygote is once again diploid.

14. Two phases: Meiosis I and Meiosis II Before Meiosis
1. Every chromosome is copied
2. Centromeres hold the chromosomes pairs together
Meiosis I
A. The chromosome pairs line up in the center of the cell
B. The pairs separate and move to opposite ends of the cell
C. Two cells form each with only half of the original number of chromosomes

15. Meiosis II – The two new cells divide
A. Chromosomes line up at the center of the cell
B. Centromeres split and the chromatids separate and move to opposite ends of the cell
End of Meiosis
Four new cells are produced- 4 gametes (sex cells) - from the original parent cell.
These 4 cells have only half the chromosomes of the parent cell.
Each has only one chromosome from each original pair

16. Meiosis Parent cell – chromosome pair Chromosomes copied
1st division - pairs split
2nd division – produces 4 gamete cells with ½ the original no. of chromosomes

17. Mitosis vs. Meiosis Mitosis is cell division to produce new cells
New cells are identical to the original cell
Meiosis is cell division to produce sex cells
New cells are not identical to the original cell

18. Meiosis Poster Project:

19. Human Genetics
23 pairs of homologus chromosomes in the human cell: 46 total chromosomes
small sections of each chromosome, genes, are responsible for inheritance
Chromosomes named as numbered pairs
Pair 23 determines sex of individual
Long chromosome X, short chromosome Y
XX is Female, XY is Male

20. Sex Chromosomes
The chromosomes that carry genes that determine the sex of offspring
Eggs contain only the X chromosome
Sperm contain an X or Y chromosome

21. Cells vs. Chromosomes
Sex cells are eggs or sperm that contain ½ the number of chromosomes, including one sex chromosome
Sex chromosomes contain genes that determine the gender of offspring

22. 50:50 Chance
Male sex chromosomes are XY
Female sex chromosomes are XX

23. Sexual Reproduction Parent cells are known as sex cells or gametes
Two parent cells join together to form a new individual
Gametes (sex cells) have half the number of chromosomes in your body cells

24. Less is More
Why is it important that sex cells have ½ the number of chromosomes?
Ensure the newly formed offspring have the correct number of chromosomes (46)

25. Protein Synthesis osome
Cells use information from a gene on a chrom_________ to produce a specific protein.
osome

26. RNA
Before protein synthesis can take place a “messe____” carry the genetic code from the DNA inside the nucleus into the cytoplasm.
This genetic messenger is called ribonucleic acid or RNA
nger

27. RNA

28. DNA vs RNA DNA RNA Copy One Strand Leaves the nucleus Master Copy
Two Strands
Never leave nucleus
Copy
One Strand
Leaves the nucleus

29. Step 1 in Protein Synthesis
Messenger RNA Production

30. Step 2 in Protein Synthesis
Messenger RNA attaches to a Ribosome

31. Step 3 in Protein Synthesis
Transfer RNA attaches to a Messenger RNA

32. Step 4 in Protein Synthesis
Protein Grows

33. Chromosomes are made of DNA
The Genetic code 19
Chromosomes are made of DNA
A gene is a section of DNA that contains information for a trait/protein
The sequence of bases in DNA forms the
Genetic Code
A group of three bases (a triplet) controls
the production of a particular amino acid
The different amino acids and the order in which they are joined up determines the sort of protein being produced

34. Valine Alanine For example Codes for Codes for 21 Cytosine Adenine
Thymine
Cytosine (C)
Alanine
Codes for
Guanine (G)
Adenine (A)

35. This is known as the triplet code22
This is known as the triplet code
Each triplet codes for a specific amino acid
CGA - CAA - CCA - CCA - GCT - GGG - GAG - CCA -
Ala
Val
Gly
Gly
Arg
Pro
Leu
Gly
The amino acids are joined together in the correct
sequence to make part of a protein
Although the DNA in the nucleus specifies the amino acids and their sequence, it is in the cytoplasm that the protein build-up takes place. The DNA of the nucleus makes a single strand of messenger RNA (ribo-nucleic acid) which leaves the nucleus and builds up the protein in the cytoplasm. The RNA code is complementary, but not identical, to the nuclear DNA. Text books usually give the coding for the RNA but in this presentation it is for the DNA itself
Ala
Val
Gly
Gly
Arg
Pro
Leu
Gly

36. A sequence of triplets in the DNA molecule may
Genes 24
A sequence of triplets in the DNA molecule may
code for a complete protein
Such a sequence forms a gene
There may be a thousand or more bases in
one gene

37. How cells make proteins
During protein synthesis, the cell uses information from a gene on a chromosome to produce a specific protein
Protein synthesis takes place on the ribosomes in the cytoplasm of a cell

38. Role of RNA
RNA (ribonucleic acid) carries the genetic code from the DNA inside the nucleus to the cytoplasm
RNA is single stranded
RNA contains adenine, guanine, cytosine and uracil (instead of thymine)

39. Types of RNA
1. Messenger RNA – copies the coded message from the DNA in the nucleus and carries the message to the ribosome in the cytoplasm
2. Transfer RNA – carries amino acids to the ribosome and adds them to the growing protein

40. Protein Synthesis
1. DNA molecule “unzips” between its base pairs. RNA bases match up along one of the DNA strands. The genetic information in the DNA is transferred to the messenger RNA strand.

41. 2. Messenger RNA attaches to a ribosome and production of the protein chain begins
3. Transfer RNA attaches to the messenger RNA where they “read” the message in messenger RNA by matching up three letter codes of bases

42. 4. Protein production continues until the ribosome reaches a three letter code that acts as a stop sign. The ribosome then releases the completed protein.

43. Protein Synthesis Overview
The cell uses information from a gene on a chromosome to produce a specific protein

44. Mutation

45. Mutation nge tein type Mutation means “cha_____” in Latin
Mutation can cause a cell to produce an incorrect pro____ during protein synthesis.
As a result, the organism’s trait, or pheno____, may be different from what it normally would have been.
nge
tein
type

46. Chp. 4 Review Jeopardy Games
Full Chapter Review:
Partial Review (Mainly Section 1&2, some 3):