5 Chromosomes

7/30/2019 5 Chromosomes

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Chromosomes

Basic makeup of a chromosome

.

1. DNA (deoxyribose nucleic acid)

2. Protein Histone

This complex of DNA and Protein is called

Chromatin


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Chromosome Structure

chromosomes (enhances

stability)

Centromere: It bindsCentromere

e c roma s oge er

Chromatids: two halves

of each chromosome. Chromatids or Sister chromatids


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Chromosomes classification

Homologous Chromosomes

These are identical chromosomes that exist in airsin diploid organisms

Identical gene location and centromere placement

Different alleles


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Locus for

flower color

genes

Homologous

pair of

chromosomes

Allele w Allele W

chromosomes are

of a single

chromatids and at

other times consisto

matids

One chromosome One chromosome

of two chromatids

Twoch


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Chromatids

only during mitosis or meiosis.

Identical gene location and centromere

placement

Identical allele before crossover

Human Male Karyotype

Homologous chromosomes


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Human Karyotype during metaphase

Homologous Chromosomes

Sister Chromatids

Chromosomes

Species Sci. Name 2n n

Cattle Bos taurus 60 30

Dog Canis familiaris 78 39

Horse Equus caballus 64 32

Human Homo sapiens 46 23

Black bread mold Aspergillus nidulans 16 8

Tobacco Nicotiana tabacum 48 24

Maize Zea mays 20 10

Soybean Glycine max 40 20

Cotton Gossypium hirsutum 52 26

Wheat Triticum aestivum 42 21


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Why is it impossible for

organism from different

genera to reproduce?

Polyploidy

Presence of more than two sets ofchromosomes


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Most eukaryotic organisms are haploid

-chromosomes

Human = 2n (n = 23) = 46

Homologous chromosomes present

-chromosomes

Human = n = 23No homologous chromosomes

Mutations based on

chromosome number

Aneuploidy change in the number of individual

Polyploidy- change in the number of chromosome sets


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Aneupolidy

Animals

Aneupoloidy typically alter the phenotypedrastically and are commonly lethal in animalsand plants.

of all spontaneous abortions (miscarry), withaneuploidy accounting for most of them.

Only 2% of fetus with aneuploidy survive

Down Syndrome

trisomoy in humans.

Trisomy of chromosome 21

Frequency = 1:800 births


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Down Syndrome

Down Syndrome

Conditions

Very similar amongindividuals

Round heads and flatfaces

Short

Retarded physicaland mentaldevelopment


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Down Syndrome

1:1000 at 30

1:100 at 40

Other Trisomy in humans

Severe retardation

Most die at age of 1

Trisom 13 Patau s ndroms 90% die before age 3


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Aneuploidy

Plants

Has been observed in some

plants

x Tobacco

x ven ng pr mrose

x Jimson weed

Trisomy

Jimson weed =

x 12 trisomicconditions have

been observedx Each changes alters

the phenotype

Rice Trisomic for the

longer chromosomesgrow slower


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Polyploidy

Autopoloidy all chromosome sets are from singlespec es

Allopolyploidy chromosome sets are from two ormore species

Polyploidy

,and pentaploids (5n).

40% of flowering plants and 70 to 80% ofgrasses are polyploids

Wheat, oats, cotton, potato, and sugar cane arepolyploids

No birds


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Autopolyploidy

Ex. No cell division of 2n organism in

mitosis

Autotriploid = 3n

Ex. No cell division after Meiosis II and fuse

with haploid gamete

Autopolyploidy

2n = 22

3n =33

Watermelon


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Allopolyploidy

P1 ABC P2 GHI

F1 = ABCGHI - sterile

xNo chromosome pairs

x are y ave no ce v s on n m os s anproduce viable seed

xAllotetraploid = AABBCCGGHHIINormal gametes

What is purpose of ployploidy

thus many polyploids are larger than diploids.

Potato autopolyploid 4n 48

Peanut Autopolyploid 4n 40

Sweet otato Auto ol loid 6n 90

Tobacco Allopolyploid 4n 48

Cotton Allopolyploid 4n 52

Wheat Allopolyploid 6n 42

Strawberry Allopolyploid 8n 56

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5 Chromosomes