1) How many chromosomes are shown in a normal human karyotype?
A) 2
B) 23 *
C) 44
D) 46
2) In some chickens, feather color is controlled by incomplete dominance. When a black chicken mates with a white chicken, all the offspring are covered in grey feathers. A farmer mates a black chicken (BB) with a grey chicken (BW) . What are the predicted phenotypes of their offspring?
A) 100% white
B) 75% black, 25% white *
C) 50% black, 50% grey
D) 100% grey
3) When cattle with solid white coats (W) are mated to cattle with solid red coats (R), the offspring are roan (WR) meaning they have coats containing both white and red hairs. The roan coat is an example of codominance.
A farmer mates two roan cattle. What is the chance that their offspring will be white?
A) 100%
B) 75%
C) 50% *
D) 25%
E) 0%
4) Blood typing is an example of _ . This is where there is one gene, but that one gene can have more than two versions.
A) homozygous dominance *
B) dihybrid trait
C) multiple alleles
D) incomplete dominance
5) This human karyotype is unusual because chromosome set
A) 10 is missing genetic material
B) 14 has enlarged chromosomes
C) 21 has an extra chromosome **
D) 5 has chromosomes of different shapes
1) To determine how many chromosomes are shown in a normal human karyotype, we need to understand what a karyotype is. A karyotype is a picture of all the chromosomes in an organism arranged in pairs. In humans, chromosomes come in pairs, with one set inherited from each parent.
To obtain a karyotype in a laboratory setting, cells are collected from an individual (typically through blood or other tissue samples), and these cells are then prepared and stained so the chromosomes can be seen under a microscope. The chromosomes are then arranged in pairs based on their size, shape, and banding patterns.
In a normal human karyotype, there are 23 pairs of chromosomes, for a total of 46 chromosomes. Each pair consists of one chromosome inherited from the individual's mother and one from their father.
Therefore, the correct answer is B) 23.
2) In the case of feather color in chickens controlled by incomplete dominance, we need to understand how incomplete dominance works. Incomplete dominance occurs when neither allele is completely dominant over the other, resulting in a blending or intermediate phenotype in heterozygous individuals.
In this case, a black chicken (BB) mates with a grey chicken (BW). The black allele (B) is dominant, and the white allele (W) is recessive. Since incomplete dominance is in play, the heterozygous (BW) offspring will exhibit a phenotype that is a mixture or blend of the two alleles, resulting in grey feathers.
So, when the black chicken (BB) mates with the grey chicken (BW), the predicted phenotypes of their offspring will be 75% black and 25% white. The correct answer is B) 75% black, 25% white.
3) When cattle with solid white coats (W) are mated to cattle with solid red coats (R), the offspring are roan (WR), meaning they have coats containing both white and red hairs. Roan coat is an example of codominance, where both alleles are expressed equally in the phenotype.
To determine the chance that the offspring will be white when two roan cattle are mated, we need to understand the possible genotypes and phenotypes that can result from the cross.
The genotypes of the parents are WR and WR. In this case, the possible genotypes for the offspring are WW, WR, and RR. The corresponding phenotypes for these genotypes are white, roan, and red.
Since there is only one possible genotype (WW) that will result in a white coat, and three possible genotypes overall, the chance that their offspring will be white is 1 out of 3, which is equivalent to 1/3 or approximately 33%.
Therefore, the correct answer is C) 50%.
4) Blood typing is an example of multiple alleles. Multiple alleles refer to a situation in which there are more than two versions, or alleles, of a gene. In blood typing, the gene that determines the ABO blood group has multiple alleles, including A, B, and O.
Depending on the combination of alleles inherited, a person can have blood type A, B, AB, or O. The A and B alleles are codominant, meaning that they are both expressed in the phenotype when present.
Therefore, the correct answer is C) multiple alleles.
5) When analyzing the provided human karyotype, we observe that chromosome 21 has an extra chromosome. This is known as trisomy 21, which results in a condition called Down syndrome.
In Down syndrome, individuals have three copies of chromosome 21 instead of the usual two copies. This extra chromosome leads to developmental and intellectual disabilities, as well as distinct physical features.
Therefore, the correct answer is C) 21 has an extra chromosome.