5.3 Genes and alleles

• Biologie
• Middelbare school
• havo
• Leerjaar 4

Theme 5 Heredity and evolution

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5.3: Genes and alleles

Put in the correct order

1. cell - chromosome - DNA - gene
2. gene - chromosome - DNA - cell
3. gene - chromosome -cell - DNA
4. gene - DNA - chromosome - cell

Zet de juiste omschrijving bij het juiste begrip.

chromosome

gene

allele

thread of DNA with hereditary information

part of a chromosome with the information of 1 characteristic

gene variant, the information in a gene

What is the difference between genotype and phenotype?

1. The phenotype is all of the DNA in your cells. The genotype are all of your visible traits
2. The genotype are all the different cells. The fenotype are alle the different genes.
3. The phenotype are all the different cells. The genotype are all the different genes.
4. The genotype is the total amount of DNA in your cells. The fenotype are all the visible traits.

Learning objectives

5.3.6 You can describe what genes and alleles are.

5.3.7 You can describe what a mutation is.

5.3.8 You can describe what cancer is.

Chromosomes

= 1 long DNA molecule rolled up in between proteins 

46 chromosomes in every nucleus

Karyotype

• 46 chromosomes
• 23 pairs of chromosomes
• 1 pair = 2 similar chromosomes of the same length, shape and with the same information
• 44  normal chromosomes 
• 2 sex chromosomes

Gene

A piece of DNA that contains the code for a one characteristic is what we call a gene.

gene = een deel van een chromosoom dat de informatie bevat van één of meer erfelijke eigenschappen)

Genes

For every hereditary trait:

one gene from your mom and 

one gene from your dad. 

DNA

Lots of base pairs together form genes

A base pair is made from 2 pieces, these are called bases.

T and A form a pair

C and G form a pair

Other pairs do not exist in DNA.

DNA is shaped like a ladder.

The ladder is built by using lots of  base pairs.

 A piece of DNA showing the base pairs

DNA codes for proteins

The order of the base pairs form a code for the production of proteins. 

gene  =  DNA code for one protein. 

For example: eye colour is determined by a gene on chromosome 15.

proteins

determine almost everything...

one gene = code for one protein

one or several proteins = one characteristic (hereditary trait)

Proteins

proteins control: 
colour, shape and functioning of your body

Genes contain the information for producing these proteins. 

Muscle cell - gene with info for producing muscle protein

Pancreas - gene with the code for insulin 

Eyes - sensory cells in your retina  the difference between the colours red and green,  colourblind.

Gene en allele

gene = piece of DNA that codes for 1 protein = 1 trait

• chromosomes are in pairs and thus genes as well

allele = one of the variants of a gene

GENE: section of DNA with complete code for a protein

Mutation

A change in the DNA

mutant = organism in which a mutation can be seen in the phenotype

Causes mutation(mutagenic influences/carcinogens)

mutations 

DNA has 4 building blocks

Nucleotides: 

ATCG (nitrogenous base)

Phosfategroup

Desoxyribose (sugargroep)

Cancer, how and why?

• Happens due to mutations
• Mutation makes cells divide continously      
• This creates a tumour:

       - Benign: divides slowly, stays at its spot

       - Malignant: divides quickly, disrupts tissues

• Metastasis > cancer cells are carried by blood/lymph. End up in different body parts and create more/new tumours

This is a karytype of.

1. sperm cell
2. egg cell
3. body cell
4. you can't tell

How many chromosome pairs do most people have in their cells?

1. 22
2. 23
3. 44
4. 46

How much hereditary material does a sex cell have compared to a normal body cell?

1. Same
2. 1/2
3. 1/4
4. twice the amount

Een allel is een variant van een

1. basepaar
2. nucleotide
3. gen
4. chromosoom

Het stukje van een DNA molecuul heeft de volgende sequentie: TGCAAA
Wat is sequentie van de tegenoverliggende nucleotiden?

1. ACGTTT
2. TTTGCA
3. TGCAAA
4. AAACGT