1. Genetics Test Review Test is Tuesday, April 21st

2. Vocabulary: Who is the “father of genetics”? What is a trait?
Gregor Mendel
What is a trait?
Physical characteristics of organisms
What is heredity?
Passing of traits from parent to offspring
What is genetics?
Scientific study of heredity

3. Vocabulary: What are genes? What are alleles?
Factors that control traits
What are alleles?
Different forms of a gene
One allele is inherited from each parent
Alleles can be dominant or recessive

4. Dominant and Recessive Alleles:
What is a dominant allele?
Always seen if present
Indicated by a capitol letter (T)
What is a recessive allele?
Masked or hidden if dominant allele is present
Indicated by a lower case letter (t)

5. Hybrid and Purebred: What is a hybrid? What is a purebred?
Organism has two different alleles for the trait – one dominant and one recessive.
What is a purebred?
Organism has two identical alleles for a trait – two recessive OR two dominant.

6. Homozygous and Heterozygous:
What is homozygous?
An organism that has two identical alleles for a trait
TT – homozygous dominant
tt – homozygous recessive
What is heterozygous?
An organism that has two different alleles for a trait
Tt – heterozygous – will show the dominant trait

7. Let’s Practice: Homozygous (HO) or Heterozygous (HE):
AA ____ Bb ____ Cc ____ Dd ____
Ee ____ ff ____ GG ____ HH ____ HO HE HE HO HE HO HE HO

8. Phenotypes and Genotypes:
What is a phenotype?
Physical appearance or visible trait
Example is flower color, stem height, etc.
What is a genotype?
The genetic makeup or allele combination
Examples are TT or Tt
Genotypes determine phenotypes

9. Determine the Phenotype:
Purple flowers are dominant to white flowers PP _____________ Pp _____________ pp _____________
Brown eyes are dominant to blue eyes BB ____________ Bb ____________ bb ____________
Purple
Brown
Purple
Brown
White
Blue

10. For each phenotype list the genotype:
Straight hair is dominant to curly. ____________ straight ____________ straight ____________ curly
Pointed heads are dominant to round heads. ____________ pointed ____________ pointed ____________ round SS PP Ss Pp ss pp

11. What are Punnett Squares?
chart that shows all possible combinations of alleles that can result from a genetic cross. Used to determine the probability of a particular outcome. The probability is the likeliness that an event will occur.

12. Punnett Square Practice:
In pea plants, purple flowers are dominant over white flowers, which are recessive. Cross a homozygous dominant parent with a homozygous recessive parent. What is the outcome for this cross?
________ x ________ PP pp
P P p Pp Pp Pp Pp
100% Purple Flowers

13. What does the term codominace mean?
Both alleles of a gene pair are equally dominant.
Neither allele is dominant or recessive to the other and as a result both alleles are expressed in a heterozygous offspring.

14. Punnett Square for Codominance:
Curly Hair CC X
Straight Hair SS
Curly and Straight Hair CS C C S CS CS
100% mixed curly and straight hair (CS) CS CS S

15. What does the term Incomplete Dominance mean?
One allele of a gene pair is only partially dominant over the other.
In these cases an intermediate form of the trait is expressed in heterozygous organisms.
Often seen in flowers.

16. Punnett Square for Incomplete Dominance:
Black mouse BB
White mouse bb X
Gray mouse Bb B B
100% gray mice (Bb) b Bb Bb Bb Bb b

17. What are sex-linked traits?
Traits that are controlled by genes located on the sex chromosomes (X or Y).
These traits are more common in males than females.
Females: XX
Males: XY

18. Female & Male Genotypes:
What is the genotype for a female? XX
What is the genotype for a male? XY

19. Sex Linked Example: Girls = XX Boys = XY XH XH XHXh XHXh Xh XHYØ XHYØ
Consider a case where hemophilia is a recessive disorder that is inherited on the X chromosome. Complete the Punnett Square to find out the results of the offspring if the mom does not have hemophilia and the dad has hemophilia. XH XH
100% the daughters will be carriers (XHXh), but will not have hemophilia.
100% of the sons will not have hemophilia (XHYØ)
XHXh
XHXh Xh
XHYØ
XHYØ YØ

20. What are multiple alleles?
Traits that are controlled by three or more alleles.
Even though more than two alleles exist for a particular trait, humans only carry two at a time.
ABO Blood Type is a good example!

21. ABO Blood Type: B O AB AO A BO OO O
Consider a family where the mother is blood type B and the father is blood type A. Is it possible for them to have a blood type O baby? Why or why not? Set up a Punnett Square to support your answer. B O
Yes, it is possible for the baby to have blood type O, if the mother’s genotype is BO and the father’s genotype is AO. AB AO A BO OO O

22. What is a pedigree used for?
A pedigree is a chart or “family tree” that tracks which members of a family have a particular trait.

23. What is the shape of DNA?
Double Helix

24. How do the nitrogen bases in DNA pair?
Adenine pairs with Thymine
Guanine pairs with Thymine

25. What is a nucleotide?
A molecule made up of a nitrogen base, a sugar, and a phosphate group.

26. Why are Watson, Crick, and Franklin so important?
Watson and Crick built a model that showed how the smaller molecules of DNA bond together and form a double helix.
Franklin used X-rays to study DNA, which indicated that DNA has a helix shape.

27. What is DNA replication?
DNA replication is the process of copying a DNA molecule to make another DNA molecule.
Steps of DNA replication:
DNA strand separates and nitrogen bases are exposed.
Nucleotides move into place and form new nitrogen base pairs.
Two identical strands of DNA are produced.

28. DNA Replication:
Determine the other DNA strand that forms during DNA replication:
Original strand: A T T C G C G A T A G C
Other strand: T A A G C G C T A T C G
Original strand: C G A A T T G G C A C C
Other strand: G C T T A A C C G T G G

29. What are the differences between DNA and RNA?
2 strands
Sugar – deoxyribose
Nitrogen bases – A, T, G, C
Pairing of bases
A with T
G with C
RNA
1 strand
Sugar – ribose
Nitrogen bases – A, U, G, C
Pairing of bases
A with U
G with C
*Uracil replaces Thymine

30. What are the function of mRNA, tRNA, and rRNA?
Messenger (mRNA): carries coded instructions for protein synthesis.
Transfer (tRNA): carries specific amino acids to ribosomes during protein assembly.
Ribosomal (rRNA): helps form chemical bonds that attach one amino acid to the next.

31. Genetic Code: What is the genetic code?
The order of nitrogen bases along a gene forms a genetic code that specifies what type of protein will be produced. The type of protein produced determines the trait!
What are the building blocks of protein?
A group of three nitrogen bases codes for a specific amino acid.

32. What are the steps of protein synthesis?
DNA “unzips” between the nitrogen base pairs.
Genetic information from DNA is copied by the mRNA which leaves the nucleus and attaches to a ribosome in the cytoplasm.
Transfer RNA (tRNA) picks up amino acids according to the mRNA code of nitrogen bases.
Each tRNA molecule attaches the amino acid to the growing protein chain.

33. What is TRANSCRIPTION?
The process by which mRNA is made from DNA. It occurs in the nucleus.

34. What is TRANSLATION?
Translation occurs in the cytoplasm, specifically on the ribosomes. The mRNA made in the nucleus travels out to the ribosome to carry the message of the DNA. Translation is the process of making a protein from RNA.

35. Identify the following in protein synthesis: tRNA, mRNA, protein chain, ribosome, and amino acid4 3 1 5
Ribosome 2

36. How To Read A Codon Chart:
Codon: series of three nitrogen bases on mRNA
1. When looking at the chart, the first letter in the codon is located on the left hand side of the chart.
2. The second letter is at the top of the chart. Find when these two letters intersect.
3. Then look at the third letter. It is found on the right hand side of the chart, in the box where one and two intersect.
4. This is the name of the amino acid that is made when that codon is read during protein synthesis.

37. Suppose one strand of DNA has the following nitrogen base sequence: TAC CGC TCC GCC ACT
What would be the order of nitrogen bases on the other strand of DNA?
What would be the order of nitrogen bases on mRNA that would be transcribed (copied) from the initial DNA sequence? (TAC CGC TCC GCC ACT)
Using this mRNA sequence and the genetic code, what amino acids, in order, would be included in the protein chain? (you can write the 3-letter abbreviation for each amino acid)
Would any additional amino acids be attached to this particular protein chain? Explain.
ATG GCG AGG CGG TGA
AUG GCG AGG CGG UGA
MET ALA ARG ARG STOP
No, because the protein chain ends with a stop codon.

38. Suppose one strand of DNA has the following nitrogen base sequence: CCC ATA ATG AAA ATC
What would be the order of nitrogen bases on the other strand of DNA?
What would be the order of nitrogen bases on mRNA that would be transcribed (copied) from the initial DNA sequence? (CCC ATA ATG AAA ATC)
Using this mRNA sequence and the genetic code, what amino acids, in order, would be included in the protein chain? (you can write the 3-letter abbreviation for each amino acid)
Would any additional amino acids be attached to this particular protein chain? Explain.
GGG TAT TAC TTT TAG
GGG UAU UAC UUU UAG
GLY TYR TYR PHE STOP
No, because the protein chain ends with a stop codon.

39. What is a mutation?
A change in the nucleotide sequence of a gene, which is a mistake that occurs in one gene of a chromosome. This causes the cell to produce an incorrect protein, which results in a different physical trait or phenotype.

40. Identify the type of mutation:
The mice ran away.
Substitution Mutation:
one nitrogen base is replaced by
a different nitrogen base
The rice ran away.
Deletion Mutation:
one or more nitrogen bases are
left out of the DNA sequence
Thei cera naway.
Insertion Mutation:
one or more nitrogen bases
are added to the DNA
The migukce ran away.