1. Unit 7 Meiosis and Mendel
Genetics and Inheritance
Quiz Date: Jan. 11 /12
Test Date: Jan. 18/19

2. UNIT 8 - INTRODUCTION TO GENETICS
Although the resemblance between generations of organisms had been noted for thousands of years, it wasn’t until the 1800s that scientific studies were carried out to develop an explanation for this. Today we know that we resemble our parents because of _______________, which is the set of characteristics we receive from ______________________. The study of heredity is known as _________________.
heredity
our parents
genetics

4. I. SEXUAL REPRODUCTION & MEIOSIS (pp. 275-278)
In sexual reproduction, an egg and sperm cell fuse together to create a fertilized egg or _______________.
zygote

5. A. Chromosome Number Body 46 Diploid 2n double 23 Mom Dad
1. Somatic Cells - _____________ cells
Human somatic cells contain ________ chromosomes
______________ or ________ meaning they contain a ____________ set of chromosomes, half ( _____ ) from _________ and half from ________.
“Matching” chromosomes known as ____________________.
made up of a copy of a chromosome from each parent, with the same ___________, but they are ____________________.
Somatic cells use ___________ for growth, development, renewal, and repair 46
Diploid 2n
double 23
Dad
Mom
Homologous pairs
genes
not identical
mitosis

6. Homologous Chromosomes

7. GAMETES n Egg Sperm 2. Gametes - ___________ and _______________ cells
Human gametes contain ______ chromosomes.
______________ or ______ meaning there is _____ set of instructions for each ______.
When gametes fuse together in _____________________, the ________________ produced is _____________ and has _______ chromosomes.
Gametes are produced by a process called __________, rather than mitosis
Sperm 23
Haploid n
one
gene
fertilization
zygote
diploid 46
meiosis

8. Haploid vs. Diploid
Karyotypes

10. B. Meiosis S 4 1/2 non-identical
Special type of cell division that only occurs in specialized germ cells (sex cells) in ____________ of females and ______________ of males.
Before meiosis, DNA is replicated once (during ______ phase of ________________)…
…But during meiosis cell divides ________________, resulting in ______ cells with _______ the original chromosome number.
Unlike mitosis which produces identical cells, meiosis produces genetically _____________ cells.
ovaries
testes S
interphase
2X, two times 4
1/2
non-identical

11. Identical somatic cells
Unique gametes

12. Meiosis occurs in two stages:

13. 1. Meiosis I Prophase I Homologous pairs tetrad
Unlike in prophase of mitosis, In prophase I___________________________ come together and stick to each other to form a ______________.
Homologous pairs
tetrad

14. Meiosis I Sister chromatid Non-sister homologue Genetic variation
Crossing Over
Exchange of genetic information between a ________________________________ with its ___________________________________.
Occurs very frequently
Allows for __________________________.
Sister chromatid
Non-sister homologue
Genetic variation

15. Meiosis I Metaphase I Anaphase I Tetrads Two sister chromatids
_____________________________ align in equator of cell
Each homologue consists of _______________________________________.
Anaphase I
__________________________________________ are pulled apart
_________________, _________________________ still intact
Tetrads
Two sister chromatids
Homologous pairs
Centromeres
Sister chromatids

17. Meiosis I 23 Telophase I Sister chromatids haploid
Two cells are formed, each with _______ chromosomes
Each chromosome still composed of two ___________________
Two cells produced at the end of meiosis I are _______________ because______________________ 23
Sister chromatids
haploid
There are no homologous pairs present

18. MEIOSIS II

19. 2. Meiosis II Gametes replication Sister chromatids 4 1/2
Continues with the two cells formed moving directly into prophase II without any further _____________________ of DNA.
In anaphase II, ______________________ are pulled apart.
Two new cells are formed from each of the two cells formed in meiosis I, resulting in a total of ___________ new cells, each with ____________the original number of chromosomes.
Cells produced are called ____________________.
replication
Sister chromatids 4
1/2
Gametes

20. MEIOSIS In females, process is known as ________________________.
In males, process is known as _________________________.
oogenesis
spermatogenesis

21. 3. Oogenesis vs. spermatogenesis
Spermatogenesis: Males produce 4 viable sperm cells
Begins:
____________
Ends:
___________
puberty
death

22. 3. Oogenesis vs. spermatogenesis
Oogenesis: Females produce only one egg and 3 polar bodies
Begins:
___________
Ends:
Before birth
menopause

23. II. HISTORY OF GENETICS (pp. 263-270)
A. Gregor Mendel
Known as the “Father of _______________”
Famous for his experiments with ________ plants.
Genetics
pea

24. Mendel P characters pureline, purebred
Used true-breeding pea plants, which means ________________________; characteristics always show. Known as the ____________ generation.
Studied seven ______________, including plant height, seed color, flower color, etc.
A character is an ______________________________.
A trait is a variant of a character
Example: Eye color is a character, brown eyes or blue eyes are traits
pureline, purebred P
characters
Inherited characteristic

25. Mendel same Self-pollination Cross-pollination
Pea plants cross-pollinate, meaning pollen from one plant fertilizes an egg from another, but they can also self-pollinate, meaning pollen can fertilize egg from ______________ plant. Mendel controlled the fertilization process of the pea plants by preventing __________________________________ and controlling ___________________________________.
same
Self-pollination
Cross-pollination

26. Pea Traits Studied

27. True-breeding B. Mendel’s Results True-breeding TT (tall) x tt (short)
P generation – Crossed __________________ plants with one trait with ________________ plants with the other.
For example, _____________________________________________
F1 generation – Offspring produced from _________________. In F1, one trait ____________. For example, tall plants X short plants = __________________________.
F2 generation – Offspring produced from _________________. In F2, trait that disappeared in F reappeared in __________ of the offspring; the other ¾ showed _____________________________.
True-breeding
TT (tall) x tt (short)
P X P
disappeared
All tall plants
F1 X F1
1/4
Dominant trait

29. Mendel’s Principles genes DNA trait
C. Mendel’s Principles – After analyzing his results carefully, Mendel formed conclusions that increased understanding of inheritance and opened the door for the study of genetics.
Individual units called ___________ determine inheritable characteristics. A gene is a portion of ___________ that codes for a specific ____________.
genes
DNA
trait

30. Alleles and Genes

31. Mendel’s Principles parent gene versions homozygous heterozygous
For each gene, an organism inherits two alleles, one from each __________________. Alleles are different forms or ____________________ of a ___________. For any given trait,
If an organism is ___________________, its alleles are the same and the trait will be expressed.
If the alleles differ, the organism is said to be ___________________ for that character and only one allele will be expressed. The expressed allele is the ______________ allele, designated by an __________-case letter. The allele that is not expressed in a heterozygous trait is _________________, designated by a _____________-case letter. A recessive allele is only expressed when an organism is ________________.
parent
gene
versions
homozygous
heterozygous
dominant
upper
recessive
lower
homozygous

32. Mendel’s Principles
Principle of Segregation - In meiosis, the two alleles for a trait segregate (_______________). Each egg or sperm cell receives a copy of one of the two alleles present in the somatic cells of the organism. There is a _________ chance that a copy of that allele will end up in the gamete produced.
Principle of Independent Assortment – The way one pair of alleles segregates has no influence on any other pair of alleles.
separate
50%

33. Independent Assortment

35. D. Genetics Terminology
Physical
1. Phenotype - ________________ description of trait; for example, ______________
2. Genotype – Genetic make-up of an organism or set of alleles; for example, ____________________.
Tall, short
TT, Tt, heterozygous, etc..

36. Genetics Terminology R rr r RR round Rr round wrinkled
3. Application of Terminology - If round pea seeds are dominant to wrinkled pea seeds, round is designated _____ and wrinkled is designated ______.
a. Homozygous dominant
Genotype = ________; Phenotype = ________
b. Heterozygous
c. Homozygous recessive R r RR
round Rr
round rr
wrinkled

38. III. ANALYZING INHERITANCE (pp.135-137)
A. Probability
Due to the law of_______________, if you know the genotype of the parents, you can predict the likelihood of a trait occurring in the offspring. Probability can be written 3 ways. The probability of a coin coming up
heads after being flipped is (fraction) _____, (ratio) ________, or (percent) _______.
segregation
1/2
50%
1:1

39. B. Punnett Squares meiosis fertilization
A Punnett square is a tool used to predict the possible outcomes of _______________ and ____________________; in other words, a Punnett square is used to determine the probability of certain traits appearing in offspring.
meiosis
fertilization

40. Punnett Practice Monohybrid crosses A-D
Must have a key
And Cross with
Each problem
For full credit

41. A: Construct a Punnett square to determine the probability of white flowers is a heterozygous purple flower (Pp) is crossed with a homozygous white flower (pp)
P=purple, p=white
1. Key:________________________
2. Cross:________________
Pp X pp
P p
50%
Probability of White flowers:___________ p
Pp pp
Pp pp

42. B: Construct a Punnett square to determine the probability of short pea plants if a homozygous tall plant (TT) is crossed with a heterozygous tall plant (Tt)
T=tall, t=short
1. Key:__________________
2. Cross:________________
TT X Tt
T T 0% T t
Probability of short pea plants:___________
Probability of tall pea plants:___________
TT TT
Tt Tt
100%

43. C: If round peas are dominant over wrinkled peas, make a Punnett square to determined the genotype and phenotype ratios of the offspring if a heterozygous plant is crossed with a homozygous recessive plant
R=round, r=wrinkled
1. Key:__________________
2. Cross:________________
Rr X rr
R r
RR:Rr:rr 0:2:2 r
Genotypic ratio:__________________
Phenotypic ratio:_________________
Rr rr
Rr rr
2:2

44. D: Use a Punnett square to determine the genotype and phenotype ratios of the offspring from a cross between a homozygous dominant yellow pea plant and a homozygous recessive green pea plant
Y=yellow, y=green
1. Key:__________________
2. Cross:________________
YY X yy
Y Y
YY:Yy:yy 0:4:0 y
Genotypic ratio:________________
Phenotypic ratio:_________________
Yy Yy
4:0

45. Dihybrid crosses
The punnett squares we have been doing are known as ____________________ crosses, meaning that only one traits has been considered at a time. In a dihybrid cross, __________ different ______________ on 2 different _____________ are analyzed.
monohybrid 2
genes
chromosomes

46. Punnett Practice dihybrid crosses A-B
Key
Cross
Punnet square

47. A. Peas homozygous for round shape and heterozygous for color are crossed with heterozygous yellow peas, heterozygous for shape
Key: R=round, r=wrinkled
Y=yellow, y=green
Cross: _____________________
Genotypic ratio:___________________________________________________________
Phenotypic ratio: _____________________________________________________

48. B. Key: G= gray body, g= black body; R=red eyes, r =black eyes
Cross: GGRr X Ggrr
What are the phenotypes of the parent fruit flies: ___________________________________________________
Genotypic ratio: ___________________________________________________
Phenotypic ratio: _____________________________________________________

49. Incomplete Dominance
Neither allele has “complete” dominance over the other; heterozygous phenotype is a blend of the 2 homozygous phenotypes
Ex: snapdragons
R = red
W = white
RW = pink

50. Incomplete Dominance: cross a pink snapdragon with a white snapdragon
1. Key: _________________________
2. Cross: ________________________
Phenotypic ratio:___________________
Genotypic ratio:____________________

51. Incomplete Dominance: cross a red snapdragon with a white snapdragon
1. Key: _________________________
2. Cross: ________________________
Phenotypic ratio:___________________
Genotypic ratio:____________________

52. Codominance
Codominance – Both alleles share dominance and are always expressed if present.
Ex: In chicken
B = black feathers
W = white feathers
BW = black AND white
feathers X

53. Codominance: cross a black chicken with a black and white chicken
1. Key: _________________________
2. Cross: ________________________
Phenotypic ratio:___________________
Genotypic ratio:____________________

54. Codominance: cross a white chicken with a black and white chicken
1. Key: _________________________
2. Cross: ________________________
Phenotypic ratio:___________________
Genotypic ratio:____________________

55. Polygenic Traits
“Many genes” ; Many traits are controlled by more than one gene; have a variety of choices for expression.
Ex: _hair color, eye color, skin tone

56. Multiple Alleles
Many genes that have more than 2 alleles, although an individual only has 2 alleles for the gene.
Ex: blood group.
There are 3 possible
alleles for this gene.

57. Suggested study questions
p. 283 (1-5, 11, 12, 17-20)