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BIOL332 > Meiosis and Mendelian Ratios > Flashcards

Meiosis and Mendelian Ratios Flashcards

1
Q

Example #1 – Jojo

A

Short Hair L_ – LL or Ll
Not Striped – aa
Orange/Black – XoXb
Intense Color – D_ – DD or Dd
Has Plaibald Spotting – Ss

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2
Q

Pleibald spotting genotypes

A

SS = NO white – melanocytes CAN migrate
***s allele = can’t spread melanocytes

Ss (Heterozygous) – Less than 50% white BUT not no whiete (Has some white – mostly around feet
- Only have 1 allele for migration

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3
Q

What controls Coat Color in cats

A

Controlled by a gene on the X chromsome

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4
Q

Coat Color in cats

A

Only come in orange or black – reast are midifications

White = absence of color

***Get different colors in fancy cats = by selection –> picking rare mutants

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5
Q

Example cat #2 (Willow)

A

Hair length – short –> L_ –> LL or Ll
Has striping – A_ –> Aa or AA
Coat color – Black –> XbY or XbXb (is grey but that means that it is really a mutaed black = coat color is black)
Coat intesity – diluted –> dd
Pleibald spotting – has no white = ss

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6
Q

Example cat #3 (Gertrude)

A

Coat color – Black –> XbY or XbXb
Pleibald –> Ss

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7
Q

Black and orange in cats

A

Co-dominet – at the organismal level they are codominant – see BOTH colors

See both orange and black NOT mix of the two = co-dominant

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8
Q

Example cat #4 (Marisa)

A

WHITE cat – SS (all white –> Means no malanocyte movement)
- White = absence of pigment –> melanocyltes can’t move = no pgment

***Has a grey tail –> means not really white cat – she is REALLY a black cat with a large white spot

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9
Q

White cat coat

A

Absence of pigment –> SS because the melanocytes can’t move = have no pigment

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10
Q

Where is there usually dark places in cat

A

Can have dark head + the rest is white because the melanocytes start in the brain stem

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11
Q

What did dad look like?

A

Pleibald:
Kittens = have less than 50% white – have Ss + some mostly white = ss
- Mom = Ss
- Means dad = Ss or ss (needs to have one s to give to kittens)

Hair length:
Mom – Short hair
All cats = short hair
Dad = Short hair OR long hair –> bevause mom has short hair + all kittens have short hair MEANS that mom + Kittens = L_ ==> means the kittens can be L_ (already can get L from mom so dad can be anything)

Stripes:
Dad = can have stripes or NOT (Aa or aa) –> Because mom has striped
- Mom = A_
- Some kittens have stripes and some do not – kittens = have aa
- Means mom is Aa (need a a to give aa cats)
- Dad is Aa or aa (striped or not) BUT needs 1 a to give aa cats

Color:
Dad = needs to be XbY because have cats that are XoXb and mom is XoXo = dad need to have Xb to give cats

Dilute:
Mom = dilute – dd
Cats – some not dilute
Dad = NOT dilute – needs to have D to give not dilute cats – Makes him DD or Dd
- No kittens are dillute = none are dd = dad doesn’t HAVE to be Dd BUT he can be

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12
Q

Two less tahn 50% white cates

A

Answer: 25%

Work through – both cats are Ss (both less tahn 50% white) –> means that when do punent square have 25% ss –> 25% are solid white

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13
Q

Test Cross

A

Test a dominent individuals (A_) that you do not know if they are homozygous domineant or heterozygous and want to figure out their genotype –> CROSS them with a recessive individual and look at offspring

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14
Q
A

0% of cats will have long hair

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15
Q
A

50%

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16
Q

Galton

A

Statistician – described correlations and regressions towards the mean

- Firgured out finger prints ate unique to indivual -- this was right 
- Decribed weather patterns 
- Vocal to sat traits are blended -- "traits are blended through generations -- wrong"
- Considered the father of Eugentioccs -- wrong about this  ***Came up with idea of nature Vs. Nurture -- is it envirnment or genetocs
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17
Q

Eugentics

A

The idea that we can improve humanity by controlled breeding

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18
Q

Mendelian genetics (History)

A

Look at peas

1865 – mendle published explanation on plant hybrids
- People know that offspring look like theor parents –> was thought that it was belnding of traits

THEN have mendle –> mendle comes and says that blenidng is NOT true

Mendle = father of genetics

1900 – Mendle’s work was rediscivered – becayse Galton his work was ignored for 40 years BUT was then rediscovered

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19
Q

Idea of inheritance before mende

A

People knew that offspring look like their parents BUT thought it was blend of traits

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20
Q

Mendle BIG idea

A

Said that blending of traits is not true – said that traits are discrete and hide + reappear
- Not blend
- He said that there are versions of genes (alleles)

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21
Q

Mendle experimntes

A

Established true breeding lines – showed that F1 and F2 offspring had predicatibel phenotypes

F1 = all green
F2 = 3:1 ration of green:yellow

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22
Q

True breeding line

A

Means that green = only makes Green
Yellow - only makes yellow

BUT means that they are homozygous – So green is homozygous for green and yellow is homozygous for yellow

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23
Q

Crossing true breeding lines

A

True bree + True breed –> F1

F1 X F1 –> F2

***In F1 X F1 – get predicatble genotypes

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24
Q

What did mendles F1 show

A

F1 phenotypes show dominent vs recesisbve relationships

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25
Q

What did mendles F2 genetration show

A

F2 phenotypes showed the recrance of recessive traits

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26
Q

Overall Mednles experinments showed…

A

Mendle Showed that F1 and F2 offspring had predictable ratios and phenotypes

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27
Q

Mendle Luck

A

He got lucky in the traits that he looked at
- his traits were all controlled by a single gene = follwoed a relationships
- All of his traits were on different chromosomes = no linkage

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28
Q

How did mendle support his work

A

Mendle used math + Distrubutions + probabailities to suport his work
***He did not know anything about chromosomes or DNA or genes or meisosis

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29
Q

Mendle expermnets (Dihybrid)

A

True X true

F1 X F1 –> 9:3:3:1 ratio

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30
Q

Mendel’s discoveries

A
  1. There are heretidatu determinats of a particular nature (there are genes)
  2. Genes come in pairs
  3. Alternate phenotypes of a single charachter are dtermined by different forms of these genes – there are aleles (Dominent vs. recessive alleles)
  4. Gametes contain one member of ecah gene pair (ploidy) – gametes have 1.2 of what non-gametes have
  5. Random fertalization – Law of segragation
  6. Genes controlling different traits are inheruted independley – Law of independt assortment
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31
Q

Mendle’s law of heretidaty

A
  1. Law of dominance
  2. Law of segraegation
  3. Law of Independent assortment
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32
Q

Low of Dominance

A

Some allels are dominent while others are recessive –> a heterozygous individual will display the dominant from

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33
Q

Law of segregation

A

Only 1 allele is carried in a gamete

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34
Q

Law of Independent Assortment

A

Genes of different Traits segregate independently to the gametes

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35
Q
A
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36
Q

Where can you see miosis

A

Can watch miosis with a microscope

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37
Q

Miosis stages

A

interphase –> miosis 1 (Promphase 1 –> metaphase 1 –> Anaphase 1 –> telephase 1) –> Meiososis 2 (P2 –> M2 –> A2 –> T2)

***Chromosome from mom + dad –> Double = now 2M + 2D –> P –> M –> A –> T –> Meiosis 2

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38
Q

Breaking down stages within meisosis

A

Each stage in meiosis can be broken down into additional phases

Example – porphase can consists of Leptotene + Zygotene + Pachytene + Diplotene + Diakinesis

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39
Q

Interphase

A

G1 phase (cell growth) –> followed by S phase (DNA synthesis) –> followed by G2 phase (cell growth)

***DNA replicates during interphase

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40
Q

Prophase 1

A

Chromsomes find each other and recombine – crossover happens here

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41
Q

Metaphase 1

A

Chiasma align at metaohase plate

42
Q

Turning Meiosis into punnet square

A

Top row + down the outside of cloum = have each possible gamete (4 gametes)

43
Q

Meiosis

A

Going from somatic cell –> Sperm/Egg (Going from diploid to haploid)

Overall: How do we pass down information to the next generation

44
Q

Why do we get 1:2:1 genotypic ratio from 4 gametes by 4 gametes

A

because real ratio is 2:4:2 –> that can be simplified into 1:2:1

4 X 4 (because get 4 gametes from miosis)

45
Q

Dihybrid Cross

A

When both parents are heterozygous at two different loci

46
Q

Example dihybrid Cross – LlAa X LlAa

A

Get 9:3:3:1 ratio

47
Q

How do you find possible gametes for ONE individual

A

Can make a square with Gene BY Gene

48
Q

Does One meiosis event produce all 4 gametes?

A

NO

49
Q

Law of idnepent assortment in action

A
50
Q

Predicted genotype ratios for mono and dihybird corsses

A

WILL ALWAYS BE THE SAME

Mono – Aa X Aa
1 AA:2 Aa: 1 aa

AaBb X AaBb
9A_B_: 3A_bb :3 aaB_ : 1aabb

51
Q

Predicted phenotypic ratios for mono and dihybird corsses

A

Might not always be the same – depends on the relationships of the alleles

52
Q

Chromosomes during Prophase 1

A

Always find eachother

53
Q

Mieosis schematic

A
54
Q

What is the point of mioeiss vs. mitosis

A

Mitosis = Make 2 identical cells
vs.
Mieosis = make 4 genetocally different cells that are destined to be sperm/egg (destined to be gametes)

55
Q

What is the point of sex

A

Want the next generation to be different than the current generation

56
Q

Set up of meiosis (chromosomes)

A
  1. Have homologous chromomes (one from mom and one from dada) BUT both are considered 1 chromosmes

Mom + dad chromsome = one chromsomes
- Each chromsome has many genes –> get 2 copies of all of the genes

  1. Centrosome
57
Q

Chromosme in human cells

A

23 pairs of chromosmes – each chromsomes has many genes – get two copes of all of the genes

58
Q

What is needed before meiosis

A

Need DNA replication – forms sister chromsatids

59
Q

Sister chromatids

A

Product of DNA replication – they are exact copies

60
Q

Centrosome

A

Organizes spindle

Made up of – Centrioles in the middle + microtubules around the outside

61
Q

Spindle

A

Divides nucleus

62
Q

First stage of meiosis

A

Interphase

63
Q

Interphase

A

Occurs just as the cell has been formed

At start = unreplicated chromsomes + 1 centrosome

64
Q

Normal cell

A

2 centrosomes (in interphase gets duplicated centrosomes)

DNA is loose – as go through interphase = DNA condences into chromsomes + during S phase of interphase the DNA is copies

65
Q

End of interphase

A

Have 2 centromeres + Condensed and duplicated chromsomes

66
Q

What happens during interphase

A

Centersome duplicates (1 –> 2 centrosomes)

DNA condesned into chromsomes + DNA is replicated during S phase

67
Q

Prophase 1

A

Overall: Chromosomes undergo Synapsis

Homokogous chromsomes come together + Wrap aroun each other very tightly – chromosomes swap patrts of chromsoes (undergo crossing over)
- Sections of mom switch with dad – in corssing over = combining chromsome that you get from both parents – making new chromsome to kids
- If doesn’t occur = give kids exact chromosome of mom or dad

Homologous chromsomes = identical excpet for conetnts of genes = cross over between homolgous chromsomes

68
Q

Where does crossing over occur

A

Prophase 1

69
Q

Metaphase 1

A

All chromsomes line up – meet in the middle of the cell at metaphase plate
- has indepent assortment

Other things that happen: Spindle attaches – centrosomes go to both sides of cells and spindle attaches to centromere at each pair of Homolgous chromosomes

70
Q

Chromsomes orineting at Metaphase 1

A

Align via indepent assortment – for 4 chromsomes –> There are 4 ways that they can align

***THIS IS A SOURCE OF VARIATION

71
Q

Sources of variation in Mieosis

A

Crossing over (Prophase 1)
Independent Assortment (Metaphase 1)

72
Q

Counting ways that chromsomes can arrange in independent assortment

A

2^pairs – gives you the number of ways that chromsomes can arrange in indepent orientation in metaohase 1

Example – 3 Homolgous Chromsomes –> 2^3 = 8 ways

73
Q

Anaphase 1

A

Pull Homlogous chromsomes apart – Homolgous chromes go to either cell

74
Q

Telephase 1

A

Reform new nuceli

75
Q

Cytokenesis

A

Divide rest of cell

Meiosis = technically dividing of nucelus

76
Q

Prophase 2

A

No more crossing over

77
Q

Metaphase 2

A

Chromsomes line uo again in teh middle and spindle attaches to centromeres

78
Q

Anaphase 2

A

Each chromsomes is pulled to either side

79
Q

Telephase 2 + cytokenesis

A

Create 4 daughter cells

80
Q

Meiosis (overall)

A

Start = 4 chromomsomes (2 Homologous chromsomes)

END = 4 cells – each with 2 cheromsomes

***ALL OF THE DAUGHTER CELLS ARE DIFFERENT THAN ORIGINAL CELL + HAVE 1/2 THE AMOUNT OF DNA THAN THE ORGINAL CELL DID
- Daughter cells will fertlize the egg or will be the egg (Start again and get a new organism thorugh mitosis)

81
Q

Complete domninace/recessive relationships

A

Means that homozygotes and heterozygots for comepltley dominent allels will show the same phenotypes

Aa or AA = same phenotype IF A is completley dominent over a

***Dominent allele = usually uppercase; recessive allele = lower case

82
Q

Deducing genotype (dominent vs recessive) in complete recesisve/dominent relationships

A

Can easily deduce the genotype for receissive trait because it must be homozygous recessive (must be aa) BUT can only partially deduce the geotype for dominenat (because it can be AA or Aa)

***can write as A_ to show uncertainty

83
Q

Sex chromosomes

A

X and Y – contrubute to sex determineration pathways of an organisms
- They contain genes that contrubute to sex determinaton pathways

***They are always considered to be a set BUT they can be non-homogous

XX = homolgous
XY = non-homologous (BUT the still follow the rules of homolgous chromsomes during mitosis + considered to be a set

XX = Female
XY = Male

84
Q

Genes on sex chromsomes

A

They contain genes that contribute to sex deterimination pathways BUT they also have genes for other pathays

***Different genes are found on sex chromsomes

85
Q

Autosomes

A

All other cgromsomes that are not sex chromsomes

86
Q

Sex Chromosomes Examples

A

Coat color in Cats

Xb –> Black
Xo –> orange

O/B = 2 alleles for the same gene

XoXo OR xoY –> Organe
XbXb OR XbY –> Black

Unique in trait = XbXo -> mix of orange and black
***NOTE all Mix black and orange cats = female

87
Q

Male Sex chromosome traits

A

Males = only have 1 X chromsome = if the trait is controled by the X chromsome then only need 1 allele to have the trait

Example – only nee 1 Xb or 1 Xo for coat color

88
Q

Co-dominence

A

When both alleles are present in heterozygote = leads to both phenotypes
- Both phenotypes are present in a heterozygote

Example
XoXb –> get a cat with BOTH orange and BLACK (NOT a blend of teh two colors see each one sperateley)

89
Q

Incomplete dominance

A

Incomplete dominant alleles lead to a phenotyope that is somewhere in the middle between either allele
(in heterozygote when both alleles are present = get a phenotype that is in between the two)
- Phenotype of teh heterozygote = somewhere in the middle
***relationship vteween alleles is neither completely dominent vs. recessive

90
Q

Melanocytes

A

Cells that produce pigment in fur
***Absense of melanocytes in skin = means no pigment in fur

***During fetal development – melanocytes orginate in brainstem and then migrate down gead and spinal cord –> THEN go around acros the skin
- Wrap around from back to stomach

91
Q

Incomplete Dominence example

A

Melanocyte migrate in cats (pleibald spotting)

S allele = inhibits cell migartion – is incompletley dominent over the s allele
- s allele = promotes full cell migration

SS = mostly white –> because have NO melanocyte migration = no pigments
- Have large patches in skin that are white because thete is no pigemnt

Ss – 50% of less is which
- because S is incompletley domeinet to s – means that Ss = have some melanocyte migration BUT not the the full extent as ss BUT is more than SS
- Hetero cats = have patches of white – often in stomach + lower extremities because these are the last regions that receive melanocytes during fetal developments
- Example – Tuxedo cat –> have white paws + some white on the chest

ss – no white –> have full melanocyte migration – all of skin areas can have/produce pigment

92
Q

Co-dominence vs. Incomplete dominece

A

Co-dominence – Heterozygotes show the phenotyoes of both alleles
Example – if have a white flower + red flower = heterzygote has red and white spots
- Phenotype will have BOTH red and white

Incomplete Dominance – Heterozygotes have phenotypes that are mid-way between each homozygous alleles
Example – Red + white flower –> the heterzygous would be pink
- Phenotyoe will be neither red nor white

93
Q

What happns if have more than two alllels per gene

A

While a gene can have more than two alleles per gene –> any diplopid organisms can only have 2 alkelles corresponding to the two homolgous chromsomes

94
Q

Relationships between alles

A

Is context specific
Ex. A1 and A2 = Co-dominnet BUT A1 and A3 are incomplete dominance

A1 to A2 gives no information about A1 and A3

95
Q

Epistatsis interaction

A

The supression of the effect of one gene by another gene – describes when alleles at one locus mask the affects of an alelle at a different locus
- Type of genetic interaction that contributes to complexity if many traits

Example – The W allele in cats prevents the deposition of pigmnet and is dominent to the w allele
- Creates lack of pigment – without pigment being depsited into skin/fur -
- cat with W = might also have a dominat A for striping OR might be homozygous for non-striping (aa) –> BUT that might not show if have a W allele
- means that a cat withoiut strping might be because aa OR might be because of dominnabt W alelle
- Can can be white AND have XoY or XbY BUT shows white because it also has the dominant W gene = W masks the phenotypes of teh other genes
***Means that you can’t deddeuce these genotypes from yhe phenotypes

***The phenotyes cointrolled by some of other coloration genes are masked
-

96
Q

Pleitropy

A

The phenomona where 1 gene affects more than one trait
- One allele of of gene leads to multiple phenotypes

Example – W allele causes All white Fur + Often deaf + Often have differentley colored eyes
- The W allele leads to multiple different phenotypes
- The dominent whirte allele creates additional phenotypes

97
Q

Modifer genes

A

Some loci have major affects on phenotypes and otehrs have minor affects

Example – Agouti gene has main affect on whether a cat is striped or not
- These stripes can occur in a striaght line or in swirls –> This is a gene at a seperate locus than Agoutu that controls whether the stripes will be staight or swriled
(In exmaple the modfier gene midfies the type of stripes)

–> If have two cats – BOTH are AA or Aa (SO both are already dominent for agouti striping)
- modified Gene = TM or Tb
- TMTM OR TMTb –> Stright lines
- TbTb = swirls

98
Q

Where are rare alleles common?

A

Common in fancy breed – common due to inbreeding + Selection

99
Q

Rare alelles

A

Example – cs – temperature sensitive alleles
- Tyronsinase = involved in melanin production
cs allel = producsed different phenotypes at diffreent temperatures that is recessive to teh W-T allel

Cs = WT – produces melananin – dominent to temperature senistive allele
cs = produces melanin at low temperature NOT high

100
Q

Number of alleles possible for a gene

A

A gene can have more than 2 allleles – multiple alleles on a single gene can oproduce different phenotypes

101
Q

Lethal Alleles

A

Type of relationship between alleles

Example:
S = dominenet
s = recessive

***S allele = considered lethal!!!

SS = emoryonic lethal – affects spinal development to such a degree that the embyrp dies in uetero
Ss = Tailess
ss = tailed

BIOL332 (25 decks)

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