Topic 24 - Chromosomes and Genes

Question 1

Learning objectives

Answer 1

1. Describe chromosomes, genes and alleles.
2. Describe homologous chromosomes
3. Explain how an allele would be considered dominant or recessive
4. Determine genotypes and phenotypes of offspring from monohybrid and dihybrid crosses

Question 2

Chromosomes

Answer 2

• Chromosomes are tightly packaged chromatin

Chromatin = DNA protein complex

Question 3

Chromosome lable [heft]

Answer 3

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Question 4

Genes

Answer 4

Sections along DNA that encode for proteins
- Gene sequense determines the amino acid sequence for the protein it encodes

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Question 5

Genes and alleles

Answer 5

• On the homologuous chromosomes, the same gene is found in the same location
• The DNA sequence for the same gene on homo. chrom. may have the same variation

Question 6

Alleles

Answer 6

• Different variants of a gene due to their slight differences in DNA sequence
• Humans are diploid, so the somatic cells carry 2 alleles of a gene

Question 7

ABO blood group

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Answer 7

Deteermined by using ABO gene, containing 3 alleles
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Question 8

Genotype Vs Phenotype

Answer 8

Genotype:
- Combination of alleles for a particular gene
- Homozygous (dominant)
- Heterozygous (recessive)

Phenotype:
- The observable or measureable characteristic arising from genotype and its interaction with the environment

Question 9

Dominant vs Recessive Phenotypes [heft]

Answer 9

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Question 10

predicting the liklihood of offspring genotype and phenotype [heft]

Answer 10

Use of dihybrid cross and punnet squares
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Question 11

Dihybrid cross

Answer 11

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Question 12

Punnet square

Answer 12

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Question 13

Pedigrees

Answer 13

• Family tree including the presence or absence of a trait for each member
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