1. Genetics and Protein Synthesis
EOC Crash Course

2. Item 1: Describe the basic structure of the nucleic acids – DNA and RNA
Nucleic acids are composed of nucleotides
Nitrogen base + sugar + phosphate

3. Item 2: State the 3 structural differences between DNA and RNA
RNA contains ribose; DNA contains deoxyribose
DNA contains adenine (A), thymine (T), guanine (G), and cytosine (C) ; RNA contains A, G, C, and uracil (U)
DNA is double stranded (double helix); RNA is single stranded (single helix)

5. Item 3: Summarize the relationship between DNA, genes, and chromosomes
Chromosome – structure in the nucleus consisting of one long thread of DNA that is tightly coiled around special proteins called histones
DNA – molecule composed of nucleotides, providing the blueprint for the making of proteins
Gene – segment of DNA with the genetic code for making one protein
Chromosomes are made of DNA (and protein), in which small segments code for the amino acid sequence of a protein

7. Item 4: Summarize DNA Replication

8. Enzyme unwinds DNA
Enzymes breaks hydrogen bonds holding pairs bases together
Another enzyme bonds new DNA nucleotides to each strand
Each identical DNA molecule has ½ the original strand and ½ of a new strand
This is called the semi-conservative model

9. Item 5: Summarize Protein Synthesis
Consists of two steps:
Transcription: DNA to mRNA
Translation: mRNA to polypeptide (protein)

10. Transcription
The two complementary strands of DNA separate by breaking the hydrogen bonds between paired bases
An enzyme bonds RNA nucleotides to one DNA strand
T bonds to G and A (on DNA) bonds to U (on RNA)

11. Translation Translation begins with mRNA attaching to a ribosome
The first codon on mRNA is read (usually AUG) and the tRNA with the codon’s corresponding anticodon brings an amino acid to the ribosome
A second codon is read and a second tRNA, also carrying the corresponding amino acid, attaches to the codon

12. The two amino acids bond together
The first tRNA breaks away from the mRNA and the mRNA slides down to read the next codon
This continues until one of the stop codons is reached
The long chain of amino acids is a polypeptide

13. Amino acids bond by making peptide bonds

14. The Genetic Code

16. Item 6: Summarize steps of meiosis
Meiosis is very similar to mitosis, except
in meiosis, the daughter cells divide twice instead of once
crossing over occurs during prophase I (mixes up genes)
chromatids don’t separate until anaphase II
all 4 daughter cells are genetically different, cells are haploid (1 chromosome per pair)

17. Stages of Meiosis: Meiosis I
Prophase I: The chromosomes condense, and the nuclear envelope breaks down. crossing-over occurs
Metaphase I: Pairs of homologous chromosomes move to the equator of the cell.
Anaphase I: Homologous chromosomes move to the opposite poles of the cell
Telophase I and Cytokinesis: Chromosomes gather at the poles of the cells. the cytoplasm divides.

18. Stages of Meiosis: Meiosis II
Prophase II: A new spindle forms around the chromosomes.
Metaphase II: Chromosomes line up at the equator.
Anaphase II: Centromeres divides. Chromatids move to the opposite poles of the cells.
Telophase II and Cytokinesis: A nuclear envelope forms around each set of chromosomes. the cytoplasm divides.

19. Item 7: Summarize Mendel’s Genetics Principles
Principle of Dominant and Recessive – some genes can hide or mask others
Law of Segregation – Mendel’s genetics principle that states that genes in pairs separate during gamete formation and gene pairs are reformed during fertilization
Law of Independent Assortment – genes are inherited separately and that creates a variety in a population

20. Item 8: Complete Punnett Square to determine various modes of inheritance
Monohybrid crosses – Punnett squares showing one trait at a time
Genotype – the alleles (represented by a letter)
Phenotype – the trait seen (physical description)

21. Sex-linked – genes found on the sex chromosomes
In humans, females have 2 X chromosomes and males have 1 X chromosome and 1 Y
Most sex-lined traits are on the X chromosome
Example: hemophilia and Duchenne muscular dystrophy

22. Sex-Linked Punnett Square Example
Allele for the trait is a exponent on the X chromosome
Females have to have 2 h’s to inherit the recessive trait
Males only need 1 h to inherit the sex-linked trait

23. Multiple Alleles Punnett Square
Multiple Alleles – more than 2 alleles (forms of a gene)
Example: blood types in humans; there are 3 alleles instead of 2; A gene, B gene, and O gene

24. Codominance Punnett Squares
Codominance – 2 different alleles that are both dominant, so in a heterozygous gene pair, both traits show up
Example: A and B genes in human blood type; if a person is AB genotype, they make both A and B proteins and have blood type AB

25. Incomplete Dominance Punnett Squares
Incomplete Dominance – heterozygous genotype gives a different phenotype
Example: red and white genes in Japanese four o’clocks; a red gene paired with a white gene makes a pink flower

26. Polygenic Traits – traits controlled by more than one pair of genes; example: human skin color and human height

27. Dihybrid Crosses – Punnett squares showing 2 traits; 16 square Punnett squares

28. RrYy Dihybrid Cross Advice
On a dihybrid cross, if both parents are doubly heterozygous, the ratio in the offspring is 9:3:3:1
When determine parents’ potential gametes use the FOIL method
First of each allele
Outside alleles
Inside alleles
Last of each allele
RrYy

29. Item 9: Explain Gene Linkage
Discovered after Mendel; states that if genes are on the same chromosome and located close together, they are often inherited together
Example: red hair and freckles in people
Seems to violate Mendel’s independent principle, but as long as genes are on different chromosomes or found far apart on the same chromosome, his principle holds true

30. Item 10: Give examples of both chromosomal and gene mutations
Chromosomal mutations affect a large part of a chromosome and therefore all of the genes on that section of the chromosome
Gene mutations only affect one gene and therefore, one protein

31. Types of Mutations
Deletion mutations – deletion of a section of chromosome or one small section of a gene
Example: cystic fibrosis
Substitution mutations – one base gets substituted for another one
Example: in sickle cell

32. Nondisjunction mutations – chromatids or homologs fail to separate during meiosis; example: Down’s syndrome is caused from an extra 21st chromosome
Point mutation – affects one amino acid
Frameshift – changes a whole sequence of amino acids

33. Item 11: Explain the difference between somatic and germ cell mutations
Somatic mutations take place in cells of the body (skin, muscle, etc.) and are not passed on to offspring
germ cell mutations occur in sex cells and are passed from parent to offspring

34. Item 12: Identify Common Mutations
Sickle cell anemia – causes abnormally shaped red blood cells; autosomal recessive
Tay-Sachs – mutation in a gene for an enzyme that functions in the breakdown of a protein in neurons; autosomal recessive
Cystic fibrosis – mutation in a Cl- transport protein; autosomal recessive
Hemophilia – mutation in gene for blood clotting; sex-linked

35. More Disorders Caused by Disorders
Huntington’s – progressive nervous deterioration; symptoms don’t occur until middle age; autosomal dominant
Albinism – mutated gene for pigments; white hair; white skin; usually pink eyes

36. Mutations caused by nondisjunction
Down’s – extra 21st chromosome
Klinefelter’s – extra X chromosome; males; XXY
Turner’s – missing X chromosome; females; XO

37. Interpret pedigrees to determine how a trait is inherited in a family

38. How is this trait inherited?

39. How is this trait inherited?

40. Questions?