Inheritance a: Genes and Inheritance

• What does the nucleus of a cell contain?

  Chromosomes on which genes are located
• How many pairs of chromosomes does a diploid nucleus have?

  23 pairs of chromosomes
• What type of nuclei do gametes have?

  Haploid nuclei
• What is a gene?

  A section of a molecule of DNA that codes for a specific protein
• What is an allele?


  A specific variation of a gene for a certain characteristic

  
• How many copies of each gene do we have?

  Two copies of each gene
• From whom do we inherit our alleles?

  One allele from the mother and one from the father
• What does it mean if an individual has two different alleles for a gene?

  They are heterozygous for that gene
• What is the difference between dominant and recessive alleles?

  Dominant alleles express their trait even when only one copy is present, while recessive alleles require two copies to express their trait
• What is the phenotype?


  The observable characteristics of an individual
• What is the genotype?


  The genetic makeup of an individual

  
• What is polygenic inheritance?

  Inheritance controlled by multiple genes

  
• Why is polygenic inheritance difficult to show using genetic diagrams?

  Because of the wide range of combinations of phenotypes

  
• Give an example of a polygenic characteristic.

  Eye colour

  
• What is monohybrid inheritance?

  The inheritance of characteristics controlled by a single gene
• What is a Punnett square used for?

  To show the possible combinations of alleles in offspring
• How is the dominant allele represented in genetic diagrams?

  Using a capital letter

  
• What do family pedigree diagrams trace?

  The pattern of inheritance of a specific characteristic through generations

  
• How are males and females represented in family pedigree diagrams?

  Males are squares and females are circles

  
• What color indicates affected individuals in a family pedigree chart?

  Red

  
• What does a horizontal line between males and females in a pedigree diagram indicate?

  That they have produced children

  
• What is the probability of an offspring being tall if two heterozygous plants (Tt) are crossed?

  75%

  
• What is the probability of an offspring being short if two heterozygous plants (Tt) are crossed?

  25%
• How is the sex of a person determined?


  By one pair of chromosomes, XX in females and XY in males

  
• Who is responsible for determining the sex of the child?

  The father, as he can pass on a Y chromosome
• What is the structure of a DNA molecule?

  Two strands coiled to form a double helix

  
• What pairs with adenine in DNA?

  Thymine

  
• What pairs with guanine in DNA?

  Cytosine
• What is the role of base pairing in DNA?

  Each half of the DNA double helix acts as a template to be copied

  
• What is the structure of RNA compared to DNA?

  RNA is single-stranded and contains uracil instead of thymine

  
• What is an example of an RNA molecule?

  Messenger RNA (mRNA)

  
• What are the stages of transcription?


  DNA strands separate, nucleotides bind to one strand, and RNA polymerase joins nucleotides to form mRNA

  
• What happens during translation?

  mRNA is translated at the ribosome, codons bind with anticodons on tRNA, and peptide bonds are formed
• What is codominance?


  Both alleles within a genotype are expressed in the phenotype of an individual
• What is an example of codominance?

  Inheritance of blood group
• What are the key components of protein synthesis?


  • Transcription:

  1. DNA strands separate (by DNA helicase)

  2. Nucleotides bind to one strand by specific base pairing

  3. RNA polymerase joins nucleotides to form mRNA

  • Translation:

  1. mRNA moves to ribosome

  2. Codon on mRNA binds with anticodon on tRNA

  3. Formation of peptide bonds