1. Genetics

2. Genetics
Genetics: the study of patterns of inheritance and variations in organisms.
Genes control each trait by controlling the formation of an organism’s proteins.

3. Diploid Cells In all diploid cells there are 2 sets of chromosomes
Therefore, each cell contains two genes for each trait
The two genes can be alike or different for a trait.
For example, a gene for plant height might occur in a tall form and a short form.
The different forms of a gene are called alleles.

4. Law (Principle) of Segregation
Alleles are separated during meiosis
Each gamete only receives 1 of the 2 alleles
50:50 chance of which one it gets
Ex: 50% chance of getting tall allele
50% chance of getting short allele

6. Law (Principle) of Dominance
Some alleles are dominant whereas others are recessive.
Dominant is always expressed (seen)
Even if there is only one dominant allele
Written as a capital letter
Recessive will only show if there is not a dominant allele present
Need 2 recessive alleles to show the recessive trait
Written as a lower case letter

7. Genotype Genotype: genetic makeup of an organism
Homozygous = same alleles = TT, tt
They are either both dominant or both recessive
Heterozygous = different alleles = Tt
Shows dominant trait

8. Examples: TT represents a ____________ genotype.

9. Phenotype Phenotype: physical characteristics of an organism
TT or Tt – shows dominant characteristic
tt – shows recessive characteristic
Ex: If T is tall then:
TT = Tt = tt =

10. Dominant phenotypes
It is not possible to determine the genotype of an organism with a dominant phenotype by looking at it.

11. Phenotype vs. genotype
2 organisms can have the same phenotype but have different genotypes PP
homozygous dominant
purple Pp
heterozygous
purple

12. Punnett Squares
Used to predict the inherited traits of offspring based on the parents
A monohybrid cross examines the inheritance of one trait.
The parents are the P generation; the resulting offspring possibilities are the F1 generation.

13. T t TT Tt tt

14. Punnett squares Pp x Pp PP P p Pp P p Pp PP Pp pp Pp pp 25% 75% 50%
genotype %
phenotype PP
25%
75% P p
male / sperm Pp
50% P p
female / eggs Pp PP Pp pp
25%
25% Pp pp
1:2:1
3:1

15. Incomplete
Incomplete dominance is a condition in which one allele is not completely dominant over another
the phenotype shown is somewhere between the two extremes
usually in plants

16. Co-dominance
Co-dominance occurs when both alleles for a gene are expressed completely
the phenotype shown has evidence of both alleles
usually in animals

17. A cross between a black cat & a tan cat produces a tabby pattern (black & tan fur together). What percentage of kittens would have tan fur if a tabby cat is crossed with a black cat?

18. Multiple Alleles
Multiple allele traits have two or more variations of the same gene
only two are inherited
blood types is an example
Three alleles are A, B, and o
Four blood types
Type A—AA or Ao
Type B—BB or Bo
Type AB—AB
Type O—oo

19. If a man has type O blood and his wife has type AB, what are the possible genotypes and phenotypes for their offspring?
If a man is type A and his wife is type B, can they have a baby with type O blood? Explain your answer using a Punnett square.

20. Sex-Linked Traits
Sex-linked traits: are the result of genes that are carried on either the X or the Y chromosome.
Male: XY
Can give offspring X or Y, determines sex of offspring
Female: XX
Can only give an X to offspring

21. autosomal chromosomes
Sex chromosomes
autosomal chromosomes
sex chromosomes

22. X chromosome
more than 60 diseases traced to genes on X chromosome

23. Y chromosome
Less than 30 genes on Y chromosome
SRY

24. Sex-linked traits Hh x HH XHXh XHY XHXh XH Xh XH Y XHXH XHXH XHY XHY
sex-linked recessive
XHXh
XHY
Hh x HH
XHXh XH Xh XH Y
male / sperm
XHXH
XHXH
XHY
XHY XH Xh
female / eggs
XHY Y XH
XHXh
XHXh
XhY
XhY

25. Sex-linked traits Males only have one X Females have 2 X’s
If X has recessive trait, it will be seen
Females have 2 X’s
Need both to have recessive trait to be shown
Traits on X:
Color blindness
Hemophilia

26. Polygenic Traits
Polygenic traits are traits that are controlled by two or more genes
these traits often show a great variety of phenotypes
examples in human’s include
eye color
hair color
skin tone
predisposition to height

27. Pedigrees
a chart constructed to show an inheritance of a trait within a family through multiple generations
through the use of a pedigree the genotype and phenotype of the family members and the genetic characteristics of the trait can be tracked

28. Pedigree Symbols marriage line female male offspring lines normal
has trait

29. Pedigree Example 1
Autosomal Recessive

30. Pedigree Example 2
Autosomal Dominant

31. Pedigree Example 3
Sex-linked Recessive

32. Chromosomal Theory of Inheritance
genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns

33. Law of Independent Assortment
each pair of alleles segregates into gametes independently
4 classes of gametes are produced in equal amounts
YR, Yr, yR, yr
only true for genes on separate chromosomes
YyRr Yr Yr yR yR YR YR yr yr

34. Gene Linkage
genes that are located on the same chromosome will be inherited together
these genes travel together during gamete formation

35. Crossing Over
process in which alleles in close proximity to each other on homologous chromosomes are exchanged
this results in new combinations of alleles.
When chromosomes pair up during meiosis I, sometimes sections of the two chromosomes become crossed. The two crossed sections break off and usually reattach.
When the genes are rearranged, new combinations of alleles are formed

36. Mutations any change in the nucleotide sequence of DNA
can result from a malfunction during the process of meiosis or from exposure to a physical or a chemical agent, a mutagen
two general categories
substitution
insertion or deletion
most mutations are automatically repaired by the organism’s enzymes and therefore have no effect
if not repaired mutations can causes changes in the amino acids in proteins

37. Figure 10.22a

38. Figure 10.22b

39. If the mutant cell is a body cell (somatic cell), the daughter cells will be affected by the altered DNA
can contribute to the aging process or the development of many types of cancer
the mutation will not be passed to the offspring

40. If the mutant cell is a gamete (sex cell), the altered DNA will be passed on to the offspring
Gamete cell mutations can result in genetic disorders
If the mutation affects a single gene, it is known as a gene mutation.
Examples: sickle-cell disease, Tay-Sachs disease, Huntington’s disease, cystic fibrosis, or albinism

41. If the mutation affects a group of genes or an entire chromosome, it is know as a chromosomal mutation
Nondisjunction occurs when chromosomes do not separate during anaphase of meiosis

42. Sex chromosome examples: Klinefelter’s syndrome (male) and Turner’s syndrome (female)
Autosomal chromosome examples: Down syndrome

43. in some cases mutations are useful to organisms in different or changing environments
these mutations result in phenotypes that are favored by natural selection and increase in a population

44. Biotechnology
biotechnology is the use of genetic and cellular processes to do work to improve life

45. Genetic Engineering
the process of replacing specific genes in an organism in order to ensure that the organism expresses a desired trait
usually by taking specific genes from one organism and placing them into another organism
usually the receiving organism is a bacterium

46. scientists need to know exactly where particular genes for particular traits is on specific chromosomes
A gene map shows the relative location of each known gene on a chromosome.

47. Human Genome Project
Genome refers to all the genetic material in an organism
the Human Genome Project mapped the DNA sequence of human genes

48. Cloning an identical copy of a gene or an entire organism is produced
can result in an organism with genetic disorders or health problems

49. Gene Therapy inserting a normal gene into an absent or abnormal gene
once inserted the normal gene begins to produce the correct protein or enzyme, eliminating the cause of the disorder

50. Stem Cells
undifferentiated cells that have the potential to become specialized in structure or function
primarily found in embryos
they are also found in adult body
therapy using stem cells can replace tissue that is deficient due to disease or damage

51. Selective Breeding
method of artificially selecting and breeding only organisms with a desired trait to produce the next generation
almost all domesticated animals and most crop plants are the result of selective breeding

52. hybridization another form of selective breeding
is the choosing and breeding organisms that show strong expression for two different traits in order to produce offspring that express both traits