1. D.N.A

2. When meiosis goes wrong!
The most common malfunction in meiosis is called nondisjunction
This is when the chromosomes DO NOT come apart in anaphase

3. Nondisjunction
This can result in some gametes with too many chromosomes

4. EXAMPLE: DOWN SYNDROME
When nondisjunction occurs on the 21st chromosomes

5. 2 of our 46 chromosomes are sex chromosomes
Males have the combination XY
Females have the combination XX

6. EXAMPLE: TURNER AND KLINEFELTER’S SYNDROME
Males with Klinefelter’s Syndrome have XXY

7. EXAMPLE: TURNER AND KLINEFELTER’S SYNDROME
Individuals with Turner Syndrome have XO

8. CHECK FOR UNDERSTANDING
What is nondisjunction?
When the chromosomes don’t
separate correctly in meiosis

9. CHECK FOR UNDERSTANDING
What are the sex chromosomes for females? XX
What are the sex chromosomes for males? XY

10. CHECK FOR UNDERSTANDING
What might be the chromosomes in a male if nondisjunction occurred?
XXY
What might be the chromosomes in a female if nondisjunction occured? XO

11. Looking at Chromosomes
A Karyotype is a picture of human chromosomes
It shows all 46 chromosomes matched up with their homologous pairs
A karyotype can allow a doctor or scientist to spot any chromosome abnormalities.

12. Normal Human Karyotype
KARYOTYPES
Normal Human Karyotype
Is this a male or female?

13. Karyotyping Chromosomal Mutations Stations!
Read the descriptions of abnormalities on your worksheet
5 -6 people at each station
You will spend 5 minutes at each station
After the 5 minutes are up, you will rotate to the next station

14. Warm Up
All of the following are true about the karyotype above except:
The karyotype is of a female
The karyotype is of a female with 47 chromosomes
The karyotype is of a normal human
The karyotype is of an abnormal human

15. Quarter 2 Reflection Questions
D.N.A Objective: SWBAT explain how Mendel’s particulate mechanism differed from the blending theory of inheritance.
Quarter 2 Reflection Questions
1. How did you perform academically in Ms. Nakamura’s class for 2nd quarter?
2. How did you perform behaviorally in Ms. Nakamura’s class for 2nd quarter?
3. How can you improve for 3rd quarter?
4. How can Ms. Nakamura improve for 3rd quarter to help you have a better learning environment?

16. Genetics & The Work of Mendel

17. Gregor Mendel
Modern genetics began in the mid-1800s in an abbey garden, where a monk named Gregor Mendel documented inheritance in peas
used experimental method
used quantitative analysis
collected data & counted them
excellent example of scientific method
He studied at the University of Vienna from 1851 to 1853 where he was influenced by a physicist who encouraged experimentation and the application of mathematics to science and a botanist who aroused Mendel’s interest in the causes of variation in plants. After the university, Mendel taught at the Brunn Modern School and lived in the local monastery.
The monks at this monastery had a long tradition of interest in the breeding of plants, including peas. Around 1857, Mendel began breeding garden peas to study inheritance.

18. Mendel’s work Bred pea plants P F1 F2
Pollen transferred from white flower to stigma of purple flower
Bred pea plants
cross-pollinate true breeding parents (P)
P = parental
raised seed & then observed traits (F1)
F = filial
allowed offspring to self-pollinate & observed next generation (F2) P
anthers
removed
all purple flowers result F1
P = parents
F = filial generation
self-pollinate F2

19. Mendel collected data for 7 pea traits

20. Looking closer at Mendel’s work
true-breeding
purple-flower peas
true-breeding
white-flower peas X P
Where did
the white flowers go?
100% F1
generation
(hybrids)
purple-flower peas
In a typical breeding experiment, Mendel would cross-pollinate (hybridize) two contrasting, true-breeding pea varieties.
The true-breeding parents are the P generation and their hybrid offspring are the F1 generation.
Mendel would then allow the F1 hybrids to self-pollinate to produce an F2 generation.
White flowers came back!
self-pollinate F2
generation
3:1
75%
purple-flower peas
25%
white-flower peas

21. What did Mendel’s findings mean?
Traits come in alternative versions
purple vs. white flower color
alleles
different alleles vary in the sequence of nucleotides at the specific locus of a gene
some difference in sequence of A, T, C, G
purple-flower allele & white-flower allele are two DNA variations at flower-color locus
different versions of gene at same location on homologous chromosomes

22. Traits are inherited as discrete units
For each characteristic, an organism inherits 2 alleles, 1 from each parent
diploid organism
inherits 2 sets of chromosomes, 1 from each parent
homologous chromosomes
like having 2 editions of encyclopedia
Encyclopedia Britannica
Encyclopedia Americana
What are the advantages of being diploid?

23. What did Mendel’s findings mean?
Some traits mask others
purple & white flower colors are separate traits that do not blend
purple x white ≠ light purple
purple masked white
dominant allele
functional protein
masks other alleles
recessive allele
allele makes a malfunctioning protein
I’ll speak for both of us!
wild type allele producing functional protein
mutant allele producing malfunctioning protein
homologous chromosomes

24. Genotype vs. phenotype
Difference between how an organism “looks” & its genetics
phenotype
description of an organism’s trait
the “physical”
genotype
description of an organism’s genetic makeup F1 P X
purple
white
all purple
Explain Mendel’s results using
…dominant & recessive
…phenotype & genotype

25. PP pp Pp x Making crosses Can represent alleles as letters
flower color alleles  P or p
true-breeding purple-flower peas  PP
true-breeding white-flower peas  pp F1 P X
purple
white
all purple PP x pp Pp

26. Looking closer at Mendel’s work
true-breeding
purple-flower peas
true-breeding
white-flower peas X
phenotype P PP pp
genotype
100% F1
generation
(hybrids)
purple-flower peas
In a typical breeding experiment, Mendel would cross-pollinate (hybridize) two contrasting, true-breeding pea varieties.
The true-breeding parents are the P generation and their hybrid offspring are the F1 generation.
Mendel would then allow the F1 hybrids to self-pollinate to produce an F2 generation. Pp Pp Pp Pp
self-pollinate
75%
purple-flower peas
25%
white-flower peas
3:1 F2
generation ? ? ? ?

27. phenotype & genotype can have different ratios
Aaaaah,
phenotype & genotype can have different ratios
Punnett squares
Pp x Pp F1
generation
(hybrids) %
genotype %
phenotype P p
male / sperm PP
25%
75% Pp
50% P p
female / eggs PP Pp Pp Pp pp
25%
25% pp
1:2:1
3:1

28. Can’t tell by lookin’ at ya!
Phenotype vs. genotype
2 organisms can have the same phenotype but have different genotypes
homozygous dominant PP
purple Pp
heterozygous
purple
Can’t tell by lookin’ at ya!
How do you determine the genotype of an individual with with a dominant phenotype?

29. Test cross
Breed the dominant phenotype — the unknown genotype — with a homozygous recessive (pp) to determine the identity of the unknown allele x
How does that work?
is it PP or Pp? pp

30. How does a Test cross work?x x
Am I this?
Or am I this? PP pp Pp pp p p p p P P Pp Pp Pp Pp P p Pp Pp pp pp
100% purple
50% purple:50% white or 1:1

31. Normal Pigment chance:
D.N.A Objective: SWBAT to apply mathematical routines to determine Mendelian patterns of inheritance.
In humans the allele for albinism is recessive to the allele for normal skin pigmentation. If two heterozygtoes have children, what is the chance that a child will have normal skin pigment? What is the chance that a child will be albino? A a
AA or Aa (75%)
Normal Pigment chance:
Albino chance:
25% aa AA Aa A
If the child is normal, what is the chance that it is a carrier (heterozygous) for the albino allele?
2/3 or 67% Aa aa a

32. Mendel’s 1st law of heredityPP P
Mendel’s 1st law of heredity
Law of segregation
during meiosis, alleles segregate
homologous chromosomes separate
each allele for a trait is packaged into a separate gamete pp p Pp P p

33. Whoa! And Mendel didn’t even know DNA or genes existed!
Law of Segregation
Which stage of meiosis creates the law of segregation?
Metaphase 1
Whoa! And Mendel didn’t even know DNA or genes existed!

34. Monohybrid cross
Some of Mendel’s experiments followed the inheritance of single characters
flower color
seed color
monohybrid crosses

35. Mendel was working out many of the genetic rules!
Dihybrid cross
Other of Mendel’s experiments followed the inheritance of 2 different characters
seed color and seed shape
dihybrid crosses
Mendel was working out many of the genetic rules!

36. Dihybrid cross P YYRR yyrr 100% F1 YyRr 9:3:3:1 F2 x true-breeding
yellow, round peas
true-breeding
green, wrinkled peas x
YYRR
yyrr
Y = yellow
R = round
y = green
r = wrinkled
100% F1
generation
(hybrids)
yellow, round peas
YyRr
Wrinkled seeds in pea plants with two copies of the recessive allele are due to the accumulation of monosaccharides and excess water in seeds because of the lack of a key enzyme. The seeds wrinkle when they dry.
Both homozygous dominants and heterozygotes produce enough enzyme to convert all the monosaccharides into starch and form smooth seeds when they dry.
self-pollinate
9:3:3:1 F2
generation
9/16
yellow
round
peas
3/16
green
round
peas
3/16
yellow
wrinkled
peas
1/16
green
wrinkled
peas

37. Which system explains the data?
What’s going on here?
If genes are on different chromosomes…
how do they assort in the gametes?
together or independently?
YyRr
Is it this?
Or this?
YyRr YR yr YR Yr yR yr
Which system explains the data?

38.  Dihybrid cross YyRr x YyRr YR Yr yR yr YR Yr yR yr YYRR YYRr YyRRor
Dihybrid cross
YyRr x
YyRr
9/16
yellow
round YR Yr yR yr YR Yr yR yr 
3/16
green
round
YYRR
YYRr
YyRR
YyRr
BINGO!
YYRr
YYrr
YyRr
Yyrr
3/16
yellow
wrinkled
YyRR
YyRr
yyRR
yyRr
1/16
green
wrinkled
YyRr
Yyrr
yyRr
yyrr

39. Mendel’s 2nd law of heredity
Can you think of an exception to this?
Mendel’s 2nd law of heredity
Law of independent assortment
different loci (genes) separate into gametes independently
non-homologous chromosomes align independently
classes of gametes produced in equal amounts
YR = Yr = yR = yr
only true for genes on separate chromosomes or on same chromosome but so far apart that crossing over happens frequently
yellow
green
round
wrinkled
YyRr Yr Yr yR yR YR YR yr yr 1 : 1 : 1 : 1

40. Law of Independent Assortment
Which stage of meiosis creates the law of independent assortment?
Metaphase 1
Remember Mendel didn’t even know DNA —or genes— existed!
EXCEPTION
If genes are on same chromosome & close together
will usually be inherited together
rarely crossover separately
“linked”

41. The chromosomal basis of Mendel’s laws…
Trace the genetic events through meiosis, gamete formation & fertilization to offspring

42. Review: Mendel’s laws of heredity
Law of segregation
monohybrid cross
single trait
each allele segregates into separate gametes
established by Metaphase 1
Law of independent assortment
dihybrid (or more) cross
2 or more traits
genes on separate chromosomes assort into gametes independently
EXCEPTION
linked genes
metaphase1

43. Mendel chose peas wisely
Pea plants are good for genetic research
available in many varieties with distinct heritable features with different variations
flower color, seed color, seed shape, etc.
Mendel had strict control over which plants mated with which
each pea plant has male & female structures
pea plants can self-fertilize
Mendel could also cross-pollinate plants: moving pollen from one plant to another

44. Mendel chose peas luckily
Pea plants are good for genetic research
relatively simple genetically
most characters are controlled by a single gene with each gene having only 2 alleles,
one completely dominant over the other

45. Any Questions??