Chapter 5 Study Guide ANSWERS
1. What are traits?
ANY CHARACTERISTIC THAT AN ORGANISM CAN PASS ON TO ITS OFFSPRING THROUGH ITS
GENES.
2. What are genes?
SETS OF INFORMATION THAT CONTROL A TRAIT.
3. When we write a genotype as two capital letters (example AA) it means the organism has two
____________ alleles for that trait.
DOMINANT
4. What does it mean if an organism has a genotype that is one capital letter and one lower case
letter (example Aa)?
THE ORGANISM IS HETEROZYGOUS FOR THAT TRAIT
5. What are alleles?
THE DIFFERENT FORMS OF A GENE.
6. What is the probability of producing a tall pea plant from the cross of two heterozygous tall pea
plants?
Tt X Tt  75% CHANCE OF TALL OFFSPRING
7. What does a Punnett square show?
IT SHOWS THE POSSIBLE GENETIC COMBINATIONS FOR OFFSPRING FROM A PARTICULAR CROSS.
8. If a homozygous black Guinea pig (BB) is crossed with a homozygous white Guinea pig (bb), what
is the probability that the offspring will have black fur?
100% CHANCE OF BLACK FUR (ALL OFFSPRING WILL BE Bb)
9. What is phenotype?
AN ORGANISM’S PHYSICAL APPEARANCE OR VISIBLE TRAITS.
10. What is genotype?
AN ORGANISMS GENETIC MAKEUP OR ALLELE COMBINATIONS.
11. What does homozygous mean?
IT MEANS THE ORGANISM HAS TWO IDENTICAL ALLELES FOR A PARTICULAR TRAIT.
12. What does heterozygous mean?
IT MEANS THE ORGANISM HAS TWO DIFFERENT ALLELES FOR A PARTICULAR TRAIT.
13. What is codominance? What is the appearance like for an organism that has two different
dominant alleles for the same trait?
CODOMINANCE IS WHEN TWO ALLELES ARE NEITHER DOMINANT NOR RECESSIVE; THEREFORE
IF AN ORGANISM RECEIVES TWO DIFFERENT DOMINANT ALLELES BOTH WILL BE EXPRESSED.
14. What is the chromosome theory of inheritance?
GENES ARE CARRIED FROM PARENTS TO OFFSPRING ON CHROMOSOMES.
15. What happens during meiosis?
CELLS DIVIDE TWICE TO FORM SEX CELLS WITH HALF THE NORMAL NUMBER OF
CHROMOSOMES.
16. How does the number of chromosomes in each cell at the end of meiosis compare to the
number of chromosomes in the original cell?
17.
18.
19.
20.
21.
22.
23.
24.
25.
AT THE END OF MEIOSIS CELLS HAVE HALF THE NUMBER OF CHROMOSOMES PRESENT IN THE
ORIGINAL CELL.
What information do chromosomes contain?
THEY CONTAIN GENES, OR THE DNA SEQUENCES NEEDED TO MAKE PROTEINS.
What determines the genetic code?
THE ORDER OF BASES IN THE DNA DETERMINES THE GENETIC CODE.
How does DNA determine the amino acids in a protein?
DNA IS TRANSCRIBED TO MAKE mRNA WHICH THEN MOVES TO THE RIBOSOME WHERE
TRANSFER RNA DELIVERS THE COORESPONDING AMINO ACIDS TO CONSTRUCT THE PROTEIN.
Which base is in DNA but not RNA? Which base is in RNA but not DNA?
THYMINE (T) IS PRESENT IN DNA BUT NOT RNA, URACIL (U) IS PRESENT IN RNA BUT NOT DNA.
Where does protein synthesis take place?
AT THE RIBOSOMES
What is a mutation?
ANY CHANGE IN THE DNA SEQUENCE OR CHROMOSOME IS A MUTATION.
What makes a mutation harmful? Are all mutations harmful?
MUTATIONS ARE ONLY HARMFUL IF THEY CHANGE AN ORGANISM IN SUCH A WAY THAT IT
LESSENS THE LIKELYHOOD THAT THE ORGANISM WILL LIVE TO ADULTHOOD AND PRODUCE
OFFSPRING. NOT ALL MUTATIONS ARE HARMFUL.
If a strand of DNA is TGAG, what would the corresponding RNA strand be?
ACUC
What do messenger RNA (mRNA) and transfer RNA (tRNA) do during protein synthesis?
MESSENGER RNA IS TRANSCRIBED FROM THE DNA AND TRANSPORTS THIS MESSAGE TO THE
RIBOSOME WHERE TRANSFER RNA DELIVERS THE AMINO ACIDS THAT WILL BUILD THE ACTUAL
PROTEIN BASED ON THE CODE IN THE MESSANGER RNA.