DNA/RNA
A three-base sequence on mRNA that codes for a specific amino acid is called this.
What is a codon?
Proteins that block transcription by binding to a specific region of DNA in an operon are called this.
What are repressors?
This type of cell division produces haploid gametes.
What is meiosis?
The process where a sperm cell and egg cell combine to form a zygote.
What is fertilization?
A change in the DNA sequence is called this.
What is a mutation?
An organism with two identical alleles for a trait is described as this.
What is homozygous?
When both alleles are expressed equally in the phenotype.
What is codominance?
The process that copies a section of DNA into mRNA before protein synthesis occurs.
What is transcription?
The DNA region where a repressor binds to prevent transcription is called this.
What is the operator?
During this phase of meiosis I, homologous chromosomes align in the middle of the cell.
What is metaphase I?
Cells that contain half the normal chromosome number are called this.
What are haploid cells?
A mutation where one nucleotide is substituted but the amino acid does not change.
What is a silent mutation?
In a cross between Aa × aa, what percentage of offspring will show the recessive phenotype?
50%
Human blood type AB is an example of this inheritance pattern.
Codominance
If the DNA template strand contains the sequence TAC, what mRNA codon will be produced during transcription?
What is AUG?
Chemical changes to DNA that reduce gene expression without altering the DNA sequence are called this.
What is DNA methylation?
Two processes during meiosis that increase genetic variation among offspring.
Crossing over and independent assortment
Identical twins share this percentage of their DNA.
100%
A mutation that shifts the reading frame by inserting or deleting nucleotides.
What is a frameshift mutation?
If two heterozygous parents (Bb × Bb) are crossed, what fraction of offspring will show the recessive phenotype?
1/4
Traits controlled by many genes are described as this.
Polygenic inheritance
A mutation changes the DNA sequence TAC – GGA – TTT to TAC – GGA – ATT. Explain how this mutation could affect the protein produced.
The mutation changes a codon, which may cause a different amino acid or stop codon, altering the protein structure.
Explain how environmental factors can change gene expression without altering the DNA sequence.
Environmental signals can modify histones or DNA methylation, turning genes on or off and changing protein production.
If meiosis did not reduce chromosome number in gametes, what would happen to chromosome numbers in future generations?
The chromosome number would double each generation.
Explain why gametes must be haploid for sexual reproduction.
Fertilization restores the diploid chromosome number in the zygote.
Which type of mutation is most likely to cause the greatest change in protein structure and why?
Frameshift mutation
A child expresses a recessive trait even though neither parent shows the trait. Explain how this is possible.
Both parents are heterozygous carriers.
In incomplete dominance, red flowers crossed with white flowers produce pink offspring. Explain why.
Neither allele is completely dominant, producing an intermediate phenotype.
A section of DNA has the following sequence:
DNA: TAC – CGA – TTT – GGA
During transcription, mRNA is produced.
Explain why an error during DNA replication could affect the protein produced even though transcription and translation occur later.
An error during replication changes the DNA sequence, which changes the mRNA produced during transcription, potentially altering the codons and amino acids, resulting in a different protein.
Explain how alternative splicing allows one gene to produce multiple proteins.
Different combinations of exons are joined together, producing different mRNA molecules from the same gene.
A nondisjunction event occurs during meiosis. Predict the chromosome combinations in resulting gametes.
Some gametes will have an extra chromosome, while others will be missing that chromosome.
Explain the genetic difference between identical and fraternal twins.
Identical twins come from one zygote and share identical DNA, while fraternal twins come from two separate eggs and sperm and share about 50% of their DNA.
Explain why some mutations have no effect on phenotype.
The mutation may be silent or occur in non-coding DNA, leaving the protein unchanged.
Two parents with normal phenotypes produce a child with a recessive genetic disorder. Use allele notation to explain this.
Parents are Aa × Aa, and the child inherited aa.
Explain why polygenic traits produce a wide range of phenotypes instead of only two categories.
Multiple genes contribute additive effects to the phenotype, producing many possible trait combinations.