The gamete that contains genes contributed only by the mother is an egg
Answer:
Man's genotype: Bbdd
Woman's genotype: bbDd
First child's genotype: Bbdd
Second child's genotype: bbDd
Explanation:
This is a dihybrid cross involving two genes; one coding for eye color and the other for hair color in humans. The allele for brown eye (B) is dominant over the allele for blue eyes (b) in the first gene while the allele for dark hair (D) is dominant over the allele for red hair (d) in the second gene.
According to the question, A man with brown eyes and red hair will possibly possess genotypes: BBdd or Bbdd while a woman with blue eyes and dark hair will possibly have genotype: bbDD or bbDd. Considering the fact that they produced children with recessive traits for both gene (blue eyes and red hair), it means that they are heterozygous for their dominant trait. This means that the ideal genotype for the man is Bbdd since he will produce gametes containing B and b alleles for the first gene while the ideal genotype for the woman is bbDd since it will produce gametes with D and d allele for the second gene.
Hence, a child with brown eyes and red hair will possess genotype: Bbdd since he/she cannot receive two dominant alleles for the first gene from both parents. A child with blue eyes and dark hair will have genotype: bbDd since he/she cannot receive two dominant alleles of the second gene from both parents.
I think c and d is the best answers
A mutation which occurs when a base is introduced into the DNA sequence before transcription begins will lead to frame-shift of a single base on the DNA sequence resulting in nonfunctional protein from the transcribed mRNA.
Explanation:
This change either through addition or deletion of a single base in the codon sequences of the DNA will modify the amino acid codes and will result in nonfunctional proteins after transcription.
This mutation will just result in change of a single base, i.e., it would be added either to the enhancer region or the silencer region of the sequence before the promoter which initiates transcription.
The mRNA produced due to mutated DNA sequence after the deletion or insertion point will be read as out of frame thus resulting in nonsense protein.
