Cette leçon contient 27 diapositives, avec quiz interactifs et diapositives de texte.
La durée de la leçon est: 45 min
Éléments de cette leçon
The basics of Inheritance
TV4
Chapter 19
Inheritance
Slide 1 - Diapositive
Study the image How is this particular type of image called?
A
chromosome map
B
chromogram
C
karyogram
D
allele passport
Slide 2 - Quiz
Study the image (again)
What is true?
A
This person is male
B
This person has no chromosomal abnormalities
C
This person has too few chromosomes
D
This person has too much chromosomes
Slide 3 - Quiz
A point mutation in a gene may result in a change in the gene product (protein). THis is because a codon might have changed, resulting in the incorporation of a different amino acid in the protein structure. Explain if a karyogram could be used to detect such mutations.
Slide 4 - Question ouverte
Chromosomal abnormalities like tri- or monosomies are caused by errors occurring during meiosis 1 and/or meiosis 2. How are these errors in chromosomal distribution called?
A
Genetic recombination
B
Genetic modification
C
Non-disjunction
D
Diploidy
Slide 5 - Quiz
How many chromosomes are in the human (nuclear) genome?
A
23
B
46
C
92
D
256
Slide 6 - Quiz
What does diploid mean? How many copies are present of each chromosome? Only note a number.
Slide 7 - Question ouverte
Learning objectives
You acknowledge that genes are located on fixed locations within the genome
You can describe the difference between a gene and allele
You can explain how a difference allele dominance may result in difference in phenotype
You can explain how alleles are distributed in gametes
Slide 8 - Diapositive
Genes, alleles, loci and chromosomes
A gene encodes a protein. These proteins will result in having certain (hereditary) traits.
Every gene is located on a fixed spot on the genome. This spot is called a locus (pleural: loci).
Each gene might have different variants. A gene variant is called an allele.
Because a diploid organism has two copies of each chromosome (homologous), this organism will have two loci of each genes. These may carry the same or different alleles.
Slide 9 - Diapositive
Drag the analogous description to the proper term
A gene variant: because of mutations, differences might have emerged. Because of these differences, proteins have diverged.
A nucleotide sequence that contains conding information, used by ribosomes to synthesize proteins.
Because both the father and mother have donated a copy, an organism has two of these. Together they belong to the same pair. There are small genetic differences between the two.
A fixed locus on a chromosome. On this spot each organism (of the same species) has the same genetic information that, although small difference are present.
homologous chromosomes
allele
locus
gene
Slide 10 - Question de remorquage
Genes, alleles, loci and chromosomes
A gene encodes a protein. These proteins will result in having certain (hereditary) traits.
Every gene is located on a fixed spot on the genome. This spot is called a locus (pleural: loci).
Each gene might have different variants. A gene variant is called an allele.
Because a diploid organism has two copies of each chromosome (homologous), this organism will have two loci of each genes. These may carry the same or different alleles.
Slide 11 - Diapositive
Two alleles per locus or gene
Twee of the same alleles? HOMOZYGOUS
Twee different alleles? HETEROZYGOUS
Slide 12 - Diapositive
Study the image
What is true?
This organism is...
A
homozygous for the left gene
heterozygous for the middle gene
heterozygous for the right gen
B
heterozygous for the left gene
heterozygous for the middle gene
homozygous for the right gene
C
homozygous for the left gene
homozygous for the middle gene
heterozygous for the right gene
D
homozygous for the left gene
heterozygous for the middle gene
homozygous for the right gene
Slide 13 - Quiz
Dominance
In many cases one allele is dominant. This means that when an individual is heterozygous, only the dominant allele will be determining the phenotype.
The other allele is called recessive.
Slide 14 - Diapositive
A black guinea pig male is bred with a white guinea pig female. They get 20 individuals as offspring which are all black What allele is dominant? Explain why.
Slide 15 - Question ouverte
Chinchillas (guinea pig resembling vermin) do it differently. A black and a white specimen are bred and they get numerous offspring. In contrast to guinea pigs, all of these off spring are dark grey. Give a possible explanation for this different phenotype.
Slide 16 - Question ouverte
Incomplete dominance
Some times the recessive allele also influences the phenotype just slightly
Some times both alleles are evenly dominant in determining the phenotype
A homozygous plant with two alleles for red flowers have red flowers.
A homozygous plant with two alleles for white flowers have white flowers.
A heterozygous plant with both an allele for red flowers and for white flowers actually have pink flowers.
Because both alleles are evenly dominant, both are determining the phenotype together.
The resulting phenotype is called an intermediate phenotype.
Slide 17 - Diapositive
Letter notation for genes en alleles
Complete dominance
The letter is assigned to the gene *
dominante allele: capitol letter A
recessive allele: small letter a
Genotypes
homozygous dominant: AA
heterozygous: Aa en aA**
homozygous recessive: aa
* = if you choose a letter yourself, choose a letter that has a different capitol letter than small letter.
** = the capitol letter MUST be noted down first.
Slide 18 - Diapositive
A pea plant that has green seeds (peas) is bred with a plant with yellow seeds.
ALL offspring have green peas Wat is the genotype of both parent plants? Wat is het genotype of the offspring? Use the letter K and/org k to indicate the alleles.
Slide 19 - Question ouverte
Letter notation for genes and alleles
Co-dominance
A letter is assigned to the gene
Because both alleles are evenly dominant, both alleles get the same capitol letter. A second letter is needed to indicate the difference in alleles (in superscript)
BR = allele for red flowers
BW = allele for white flowers
Genotypes
plant with red flowers: BRBR
plant with white flowers: BWBW
plant with pink flowers: BRBW and BWBR
Slide 20 - Diapositive
A snapdragon (plant) with red flowers is bred with a snapdragon with white flowers. ALL offspring have pink flowers. What is the genotype of both parent plants? What is the genotype of the offspring? Use the letter BR and/or BW to indicate the alleles.
Slide 21 - Question ouverte
If your ear lobe is attatched to your head or not is a hereditary trait that is monogenetic. It is caused by one single gene. The allele for loose lobes is dominant.
What gametes will a heterozygous father produce?
A
100% of his spermcells are Aa
B
50% of his sperm cells are A
50% of his sperm cells are a
C
75% of his sperm celles are A
25% of his sperm cells are a
D
100% of his sperm cells are a
Slide 22 - Quiz
Segregation of alleles during meiosis
Een somatic cell is diploīd
(2n) so every gene is present twice (Pp)
A gamete is haploid (n) so every gene is present once. (P)
During meiosis 1 homologous pairs are split. Half of the daughter cells will receive one allele, the other half the other allele.
So a cell with genotype Pp that undergoes meiosis will result in having 50% of the gametes being P and the other half being p.
Slide 23 - Diapositive
A father that is heterozygous for the ear lobe gene gets a child with a mother that is also heterozygous.
What gametes do these parents produce?
A
papa: 50% A en 50% A
mama: 50% a en 50% a
B
papa: 100% Aa
mama: 100% Aa
C
papa: 50% A en 50% a
mama: 50% A en 50% a
D
papa: 75% A en 25% a
mama: 75% A en 25% a
Slide 24 - Quiz
Punnett squares
gameten of the parents along the axes of the table
in the table cells: possible genotypes of the offspring
Example
chance that a sperm cell with the recessive gene fertilises an ovum is 1/2
chance that the ovum itself has the recessive allele is 1/2
chance that zygote has both recessive genes therefore is 1/2 * 1/2 = 1/4
Slide 25 - Diapositive
Do the following assignment on paper. Take a picture of your answer and upload it here. A man that is heterozygous for the ear lone gene has a child with a woman that has attached (recessive) earlobes. Calculate the chance that the child also has attached lobes. Explain your answer with a Punnett square.
Slide 26 - Question ouverte
Learning objectives
You acknowledge that genes are located on fixed locations within the genome
You can describe the difference between a gene and allele
You can explain how a difference allele dominance may result in difference in phenotype
You can explain how alleles are distributed in gametes