How many chromosomes are found in each human body cell
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HOW MANY CHROMOSOMES ARE FOUND IN EACH HUMAN BODY CELL?. Genes do not exist free in the nucleus of a cell; they are lined up on chromosomes. Section 10.2 Summary – pages 263-273. Diploid Cells. Section 10.2 Summary – pages 263-273.

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HOW MANY CHROMOSOMES ARE FOUND IN EACH HUMAN BODY CELL?

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How many chromosomes are found in each human body cell

HOW MANY CHROMOSOMES ARE FOUND IN EACH HUMAN BODY CELL?


Section 10 2 summary pages 263 273

Genes do not exist free in the nucleus of a cell; they are lined up on chromosomes.

Section 10.2 Summary – pages 263-273


Section 10 2 summary pages 263 2731

Diploid Cells

Section 10.2 Summary – pages 263-273

  • In the body cells of animals and most plants, chromosomes occur in pairs.

  • In each pair, one you inherited from your mom, the other from your dad.

From Mom

From Dad


Section 10 2 summary pages 263 2732

Homologous Chromosomes

Section 10.2 Summary – pages 263-273

The two chromosomes of a pair are called homologous chromosomes.

Each pair of homologous chromosomes has genes for the same traits.


Section 10 2 summary pages 263 2733

Diploid Cells

Section 10.2 Summary – pages 263-273

  • A cell with two of each kind of chromosome is called a diploid cell.


Section 10 2 summary pages 263 2734

Section 10.2 Summary – pages 263-273

  • Body cells (diploid) are different from sex cells.

  • Each person can only pass on ONE of their homologous chromosomes to their young.

HUMANS = 46 CHROMOSOMES

IN THEIR BODY CELLS

Each parent passes 23 to their young, so that when the sperm and egg combine- it will equal 46 Chromosomes.


Section 10 2 summary pages 263 2735

Haploid Cells

Section 10.2 Summary – pages 263-273

  • So, sex cells CANNOT be diploid.

  • A cell containing only one of each kind of chromosome is called a haploid cell.


Section 10 2 summary pages 263 2736

Sexual Reproduction

Section 10.2 Summary – pages 263-273

Zygote


Section 10 2 summary pages 263 2737

Section 10.2 Summary – pages 263-273

Diploid and Haploid Cells

Chromosome Numbers of Common Organisms

Organism

Body Cell

Sex Cell

8

Fruit fly

4

Garden pea

14

7

Corn

20

10

Tomato

24

12

26

Leopard Frog

13

17

Apple

34

Human

46

23

Chimpanzee

48

24

Dog

78

39

1260

630

Adder’s tongue fern


How many chromosomes are found in each human body cell

In Humans, how many chromosomes would each of these cells have…..

CHEEK CELL

46

SPERM CELL

23

EGG CELL

23

NERVE CELL

46


How many chromosomes are found in each human body cell

The kind of cell division that produces sex cells (haploid) containing half the number of chromosomes as a body cell, is called meiosis.

Meiosis I

MeiosisII

Sister

chromatids

separate

Homologs

separate

Diploid

Diploid

Haploid


Meiosis cell division that makes sex cells

Meiosis: cell division that makes SEX CELLS.

Click here to see the animationhttp://www.cellsalive.com/meiosis.htm

46

It starts with a DIPLOID cell

Chromosomes Replicate

92

46

46

23

23

23

23

It ends with FOUR HAPLOID cells (not identical)


Section 10 2 summary pages 263 2738

Section 10.2 Summary – pages 263-273

Meiosis

  • These haploid cells are called sex cells— gametes.

  • Male gametes are called sperm.

  • Female gametes are called eggs.


Section 10 2 summary pages 263 2739

Section 10.2 Summary – pages 263-273

Meiosis

  • When a sperm fertilizes an egg, the resulting zygote once again has the diploid number of chromosomes.


Sect ion 10 2 summary pages 263 273

Sect ion 10.2 Summary – pages 263-273


Section 10 2 summary pages 263 27310

Interphase

Section 10.2 Summary – pages 263-273

  • Growth period in which the cell replicates its chromatin (DNA).


Meiosis i reduction division

Spindle

fibers

Nucleus

Nuclear

envelope

Meiosis I: Reduction Division


Prophase i

Prophase I

  • Chromatin coils up.

  • Spindle forms.

  • Nuclear envelope fragments.


Tetrads form in prophase i

Tetrads Form in Prophase I

Homologous chromosomes(each with sister chromatids)  

Join to form aTETRAD


Crossing over in prophase i

Crossing-Over in Prophase I

The tetrads pair so tightly that non-sister chromatids from homologous chromosomes can actually break and exchange genetic material in a process known as crossing over.


Crossing over

Crossing-Over

Crossing over can occur at any location on a chromosome, and it can occur at several locations at the same time.


Section 10 2 summary pages 263 27311

Section 10.2 Summary – pages 263-273

Metaphase I

  • In Metaphase I, the tetrads line up in the middle, or equator.

  • The centromere of each chromosome becomes attached to a spindle fiber.


Anaphase i

Anaphase I

Homologous chromosomes separate and move to opposite poles.

Sister chromatids remain

attached at their centromeres.


Telophase i

Telophase I

Nuclear envelopes reassemble.

Spindle disappears.

Cytokinesis divides cell into two.


Meiosis ii reducing chromosome number

Meiosis II: Reducing Chromosome Number

The second division in meiosis is simply a mitotic division of the products of Meiosis I.

Prophase II

Metaphase II

Telophase II

Anaphase II

4 Identical haploid cells


Prophase ii

Prophase II

Nuclear envelope fragments.

Spindle forms.


Metaphase ii

Metaphase II

Chromosomes align

along equator of cell.


Anaphase ii

Anaphase II

Equator

Pole

Sister chromatids separate and move to opposite poles.


Telophase ii

Telophase II

Nuclear envelope assembles.

Chromosomes decondense.

Spindle disappears.

Cytokinesis divides cell into two.


Results of meiosis

Results of Meiosis

Gametes (egg & sperm) form

Four haploid cells with one copy of each chromosome

One allele of each gene

Different combinations of alleles for different genes along the chromosome


Section 10 2 summary pages 263 27312

Section 10.2 Summary – pages 263-273

Nondisjunction

  • The failure of homologous chromosomes to separate properly during meiosis is called nondisjunction.

  • This would occur in Anaphase I, when homologous chromosomes are suppose to separate from each other.


Section 10 2 summary pages 263 27313

Nondisjunction

Section 10.2 Summary – pages 263-273

When a gamete with an extra chromosome is fertilized by a normal gamete, the zygote will have an extra chromosome.

  • This condition is called trisomy.

  • An example of this in humans is Downs Syndrome


Downs syndrome

Downs Syndrome

  • Extra chromosome on 21

    •1 in every 1100 live births

    •Range from mild to severe physical and mental disabilities


Section 10 2 summary pages 263 27314

Nondisjunction

Section 10.2 Summary – pages 263-273

  • Although organisms with extra chromosomes often survive, organisms lacking one or more chromosomes usually do not.

When a gamete with a missing chromosome fuses with a normal gamete during fertilization, the resulting zygote lacks a chromosome.

  • This condition is called monosomy. An example of this in humans is Turner’s Syndrome.


Turners syndrome

Turners Syndrome

  • Absence of one X chromosome

  • Occurs in 1 out of every 2,500 live female births.

  • Physical characteristics

  • No mental disability


Section 2 check

Section 2 Check

Question 1

A cell with two of each kind of chromosome is __________.

A. diploid

B. haploid

C. biploid

D. polyploid


Section 2 check1

Section 2 Check

Homologous Chromosome 4

The answer is A. The two chromosomes of each pair in a diploid cell are called homologous chromosomes. Each has genes for the same traits.

a

A

Terminal

Axial

Inflated

D

d

Constricted

T

t

Short

Tall


Section 2 check2

Section 2 Check

Question 2

Meiosis

Haploid gametes

(n=23)

What is the importance of meiosis in sexual reproduction?

Sperm Cell

Meiosis

Egg Cell

Fertilization

Diploid zygote

(2n=46)

Multicellular

diploid adults

(2n=46)

Mitosis and Development


Section 2 check3

Section 2 Check

Meiosis is cell division that produces haploid gametes. If meiosis did not occur, each generation would have twice as many chromosomes as the preceding generation.

Meiosis

Haploid gametes

(n=23)

Sperm Cell

Meiosis

Egg Cell

Fertilization

Diploid zygote

(2n=46)

Multicellular

diploid adults

(2n=46)

Mitosis and Development


Section 2 check4

Section 2 Check

Question 3

How does metaphase I of meiosis differ from metaphase of mitosis? (TX Obj 2; 10A)


Section 2 check5

Section 2 Check

During metaphase of mitosis, sister chromatids line up on the spindle's equator independent of each other. During metaphase I of meiosis, homologous chromosomes are lined up side by side as tetrads.

Centromere

Sister chromatids

Metaphase I


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