2. THE LAW OF SEGREGATION Flashcards
1
Q
- What is Hybridization?
A
- the process of interbreeding individuals
- these individuals come from genetically distinct
populations - their interbreeding produces a hybrid
- this genetic hybrid carries two different alleles of the
same gene
2
Q
- How did Mendel use Hybridization?
A
- Mendel mated 2 contrasting varieties
- both these varieties were true breeding
- he mated white and purple flowered pea plants
3
Q
- What is another name for True-breeding varieties?
A
- Homozygotes
4
Q
- What are Homozygotes (True-Breeding Varieties)?
A
- these are plants that produce offspring
WHEN THESE OFFSPRING SELF-POLLINATE:
- they are of the same variants only
5
Q
- What are the results seen in the F1 Generation when white flowered pea plants are mated with purple flowered pea plants?
A
- all the F1 Generation hybrids are purple
6
Q
- Are F1 Generation individuals heterozygotes or homozygotes?
A
- the F1 Generation individuals are hybrids
- these means they are heterozygotes
7
Q
- What is the result of mating the F1 Generation hybrids with one another?
A
- there will be a ratio of 3:1
- 3 purple flowers : 1 white flower
- these results are seen in the F2 Generation
8
Q
- When it comes to the mating of purple and white flowered Pea Plants, which trait is dominant?
A
- the purple flower colour
- the white flower colour is the recessive trait
9
Q
- What is Mendelian Inheritance?
A
- these are the certain patterns of traits
- it focuses on how these traits are passed from parents
to offspring
10
Q
- What do we call Mendel’s “Heritable Factors” nowadays?
A
- genes
11
Q
- Provide a definition for Homozygous?
A
- this is an organism with 2 identical alleles
- these alleles are identical for a specific gene
- these alleles are said to be homozygous for the gene
that is responsible for a specific character
EG: AA, aa, true breeding
12
Q
- Provide a definition for Heterozygous?
A
- this is an organism that has 2 different alleles
- these alleles are different for a specific gene
13
Q
- Provide a definition for Heterozygous?
A
- this is an organism that has 2 different alleles
- these alleles are different for a specific gene
- these alleles are said to be heterozygous for the gene
that is responsible for a specific character
EG: Aa, breeding that is not true, hybrids
14
Q
- Provide a definition for a Phenotype.
A
- this is the physical appearance of an organism
- these are the organism’s characteristics
15
Q
- What is a Genotype?
A
- this is the genetic make up of an organism
- these are the allele combination for an organism
16
Q
- What are Alleles?
A
- these are different versions of the same gene
- they are found on the same position on homologous
chromosomes - they have the same locus
- alleles are responsible for encoding the same
characteristics
17
Q
- What are Dominant Alleles?
A
- these are the alleles that are expressed in the
phenotype - these alleles are represented with a Capital Letter
18
Q
- What are Recessive Alleles?
A
WHEN THESE ALLELES ARE COMBINED WITH A DOMINANT ALLELE:
- they are not expressed in the phenotype
WHEN THESE ALLELES ARE COMBINED WITH A RECESSIVE ALLELE:
- they are expressed in the phenotype
- they are represented using a lower case letter
19
Q
- What is the pattern Mendel observed with regards to the F2 Offspring Generation?
A
- many of their characteristics followed a 3:1 inheritance
pattern
20
Q
- How many of Mendel’s Concepts explain the 3:1 Inheritance pattern he observed in the F2 Generation offspring?
A
- 4 of them
21
Q
- What is Concept 1 of the Mendel Model?
A
- there are alternative versions of genes
- these account for variations in inherited characters
22
Q
- Provide an example of Concept 1 of the Mendel Model.
A
IN PEA PLANTS:
- the gene for flower colour exists in 2 versions
- purple flowers
- or white flowers
23
Q
- What are alternative versions of a gene called?
A
- alleles
24
Q
- Where does each gene resign on a specific chromosome?
A
- each gene resides at a specific locus (position) on the
chromosome
25
25. What is Concept 2 of the Mendel Model?
FOR EACH CHARACTERISTIC / CHARACTER:
- an organism inherits 2 alleles
- it inherits 1 from each parent
26
26. What is a simple definition of a Homozygote?
- 2 alleles at a locus
- on a chromosome
- are identical
EG: true breeding plants
27
27. What is a simple definition of a Heterozygote?
- 2 alleles at a locus
- on a chromosome
- are different
EG: the F1 hybrids
28
28. What is Concept 3 of the Mendel Model?
IF THE 2 ALLELES AT A LOCUS DIFFER:
- this means that they are heterozygotes
- the dominant allele will determine the organism's
appearance
- this will show in the phenotype
- the recessive allele will have no noticeable effect on
the appearance
EXAMPLE:
- purple flowers contain a dominant trait
- white flowers contain a recessive trait
29
29. What is another name for Concept 4 of the Mendel Model?
- the Law of Segregation
- this is Mendel's 1st Law
30
30. What is the Law of Segregation?
(Mendel's 1st Law)
(Concept 4 of the Mendel Model)
THE 2 ALLELES FOR A GENE:
- separate and segregate during gamete formation
(meiosis)
- these alleles will end up in different gametes
- the alleles for a gene are responsible for the heritable
characteristics
31
31. What does the segregation of the alleles correspond
to?
- the separation of the homologous chromosomes
TO different gametes
DURING meiosis
32
32. What does each gamete (egg or sperm) have?
- they have only 1 of the 2 homologous chromosomes
from each pair
- this means that they each have only 1 of the 2 alleles
- these homologous chromosome pairs are present in
the somatic cells of an organism
33
33. Study this image well.
Does everything make sense?
- yes
34
34. What is a Punnet Square?
- it is a diagram
- it predicts the results of a genetic cross between
individuals
- the genetic makeup (genotype) of these individuals is
known
35
35. What does a Punnet Square Show?
- it shows the possible combinations of sperm and eggs
- a capital letter represents a dominant allele
- a lowercase letter represents a recessive allele
