5.2 chromosomes

• Biologie
• Middelbare school
• vwo
• Leerjaar 2

5.2 chromosomes

5.2.3 You can explain how each of the parents provides 50% of the chromosomes.

5.2.4 You can say how the sex of a human is determined by sex chromosomes.

5.2.5 You can explain how sexual reproduction causes variation in genotypes.

Every human has thousands of hereditary characteristics. The information for all of them can be found in just 46 chromosomes. You have two of each chromosome.

Chromosomes

= 1 long DNA molecule rolled up in between proteins 

46 chromosomes in every nucleus

Chromosome portret

• 44 autosomes =                        normal chromosomes 
• 2 sex chromosomes
• chromosome pair= 2 homologue chromosomes = chromosomes of a pair that are the same length and have the same genes

autosomes and sex chromosomes

male and female

male:    2 x 22 autosomes + 

                X + Y 

                = 46 chromosomes

female: 2 x 22 autosomes + 

                X + X

                 = 46 chromosomes

Different information on a chromosome pair

egg cell and sperm cell

egg cell contains 22 autosomes + X chromsome

sperm cell contains 22 autosomes + X or 22 autosomes + Y

Meiosis = a special form of cell division to create sex cells = gametes /ovum /spem cell

Sexual reproduction

• Sperm/ova are made during a special cell division: meiosis. 
• Meiosis randomly splits all chromosome pairs, giving each daughter cell only 1 of each pair.
• Lots of different chromosome combinations are possible
• During fertilization two sex cells combine, creating new chromosome pairs

Variation

WHAT

* read 5.2

** make excercises 5.2

*** check your answers

*** test yourself 5.2 in the online book

HOW

individually

in silence

NEED HELP?

1. look in the text
2. raise your hand

get to work- IN SILENCE

How many chromosome pairs does Chamaecrista fasciculata have?

(see picture)

1. 8
2. 3
3. 16
4. 20

A fruit fly has short wings and cannot fly. This is because of a mutation in chromosome number 2. Are the short wings part of the fly's genotype? And phenotype?

1. Only genotype
2. Only phenotype
3. Part of neither genotype or phenotype
4. Part of both genotype and phenotype

homework

study 5.2

do excercises 6 till 8