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WorksheetsDihybrid Punnett Square Notes & Homologous Chromosomes
Total questions: 15
Worksheet time: 8mins
In a dihybrid cross, how many different traits are examined between the two parents?
Four traits total
Three traits total
One trait only
Two traits total
During meiosis, when are homologous chromosomes separated into different cells?
Only during fertilization
Only during mitosis
During Meiosis II
During Meiosis I
Which statement best describes homologous chromosomes in a human cell?
They are identical in sequence
They come only from the mother
They carry the same genes
They are sister chromatids
If a parent has genotype YyRr, which gamete genotype is possible after meiosis?
YYRR
YyRr
Yr
yR
In dogs, Black fur (B) is dominant over blonde (b) and Spots (A) is dominant over no spots (a). Which cross most likely yields a 9:3:3:1 phenotypic ratio for fur color and spotting?
BBAA × BBAA
BbAa × BbAa
bbAA × BbAa
Bbaa × bbAa
A puppy has long hair and floppy ears. Long hair (R) is dominant to short hair (r), and floppy ears (E) is dominant to pointed ears (e). Which genotype must be true for this puppy?
RrEe
rrEE
RREe
RRee
Parents with genotypes BbAa (black, spots) and bbAa (blonde, spots) mate. What is the probability their puppy is blonde with no spots?
0
1/8
1/4
1/2
Which step should be done first when completing a dihybrid Punnett square for traits R/r and E/e?
Count genotype frequencies
Make gametes using FOIL
Combine alleles in grid
List offspring phenotypes
Two heterozygous parents for hair and ears (RrEe × RrEe) produce offspring. What is the expected proportion with short hair and pointed ears?
3/16
4/16
6/16
1/16
A dog is heterozygous black fur with pointed ears. Which genotype correctly represents this?
bbee
BbEe
BbEE
BBee
What is a karyotype?
A sequence of DNA base pairs
A photo of all chromosomes in a cell
A list of gene mutations by trait
A diagram of protein structures
How many pairs of chromosomes are typically found in a human somatic cell?
20 pairs in each cell
22 pairs in each cell
23 pairs in each cell
24 pairs in each cell
Which set of chromosomes determines biological sex in humans?
Sex chromosomes X and Y
Duplicated sister chromatids
Autosomes only number 1–22
Mitochondrial chromosomes
What term describes having only one chromosome in a homologous pair?
Monosomy in one pair
Trisomy in one pair
Polyploidy across pairs
Disomy in one pair
Trisomy 21 results from having three copies of chromosome 21. Which condition does this cause?
Turner syndrome in females
Down syndrome in humans
Klinefelter syndrome in males
Cri-du-chat in infants
