Samenvatting Biology 2havo/vwo ch5-6-8

Biology summary ch5
5.1 Pass it on!
 Inherited= receiving a genetic characteristic transmitted by a parent.
 Genotype= complete set of all inherited characteristics. (what you can’t see)
 Phenotype= set of inherited characteristics that are actually expressed. (what you
can see)
 Phenotype = genotype + environmental factors.
 Chromosome= structure inside the nucleus that contain inherited stuff.
 There are 46 chromosomes inside a fertilised egg cell. All of the cells that will grow
will each have one set of the same 46 chromosomes.
 Karyotype= a photo of all chromosomes in one cell grouped together and arranged.
 Homologous pairs= 2 chromosomes that match each other in the genes they contain.
 An egg cell and sperm cell only have 23 chromosomes each instead of 46 like other
cells.
 When and egg cell and sperm cell fuse, their chromosomes form homologous pairs.

5.2 What are the chances?
 Humans have 23 pairs of chromosomes, one of these pairs is a pair of sex
chromosomes and the other 22 are called autosomes.
 Sex chromosome= one of the 2 special chromosomes. The x and y combination
determines the gender.
 Autosome= one of the 44 regular (non-sex) chromosomes in a human.
 Boy= 2 x 22 autosomes + X + Y = 46 chromosomes
Girl= 2 x 22 autosomes + X + X = 46 chromosomes
 A sperm cell= Type 1: 22 autosomes + X = 23 chromosomes or,
Type 2: 22 autosomes + Y = 23 chromosomes.
An egg cell= 22 autosomes + X = 23 chromosomes. (only possibility)
 Male is an X and Y, Female is 2 X.




5.3 DNA and genes

,  DNA= the hereditary material in organisms.
 DNA is made up of small units called nucleotides.
 Nucleotides= consists of 3 parts; the base (with the info), a phosphate and a sugar.
Phosphate and the sugar are sort of the backbone which connects.
 There are 4 different types of nucleotides. All have the same sugar and phosphate
but a different base. There are 4 bases in total; guanine, adenine, thymine and
cytosine. Abbreviated with the letters G, A, T and C. Nucleotides line up and connect
one half of a DNA strand, two nucleotides strands make a double DNA strand. C
always binds to G and A always binds to T on the opposite strand. This is called baise
pairing.
 Base-pairing= the organisation of bases in opposite strands od DNA: A – T and G – C.
 Gene= a section of DNA that has the complete code for a single protein.
 Cell -> Nucleus -> Chromosome -> DNA -> Genes -> Nucleotides -> Base, Phosphate,
Sugar.


5.4 Inheritance
 Alleles= different forms of the same gene.
 A stands for brown eyes, a stands for blue eyes.
AA= brown eyes Aa= brown eyes aa= blue eyes
Phenotype= brown eyes Genotype= AA
 Dominant= the allele that is expressed. Always a capital letter
 Recessive= the allele that isn’t expressed or masked by the other allele. Always a
small letter
 Carrier= having a dominant, expressed allele and a recessive, masked allele.
 If you are homozygous for eye colour you have AA or aa. If you are heterozygous for
eye colour you have Aa.
 F1= first generation of offspring (children), F2 second generation (grandchildren).
 Punnet square= a table for determining genetic offspring.
Sperm (B) Sperm (B) F1 Sperm (B) Sperm (b) 

Egg cell (b) Bb (F1) Bb (F1) Egg cell (B) Bb (F2) Bb (F2)

Egg cell (b) Bb (F1) Bb (F1) Egg cell (b) Bb (F2) bb (F2)


 Probability= the chance that something will happen.




5.5 When genes change
 Mutation= a change in a chromosome or gene.