Download Lesson 63 Show Me the Genes KEY

Name ________________________________ Date ___________________ Period ___
Lesson 63- Show Me the Genes!
Read pages D47-D54 and answer the following questions.
1. How many chromosomes does each cell in the human body contain?
46
2. Look at figure 4, how do 46 chromosomes become two sets of 46?
The chromosomes copy themselves and then split apart.
3. What would happen to the number of chromosomes in each cell if copies of them were not made
before cell division?
Each time the cell divides, the number of chromosomes would be cut in half and the cells
wouldn’t have the information it needs to help the organism function.
4. What is unique about chromosome number 23?
Chromosome 23 determines gender.
5. Females have
XX
6. Males have
XY
7. What do you think scientists mean when they say, “…the 23 pairs of chromosomes behaved just
like the genes in Mendel’s models?”
The offspring receive half of their chromosomes from each parent just like in Mendel’s
model.
8. We know that parents make “copies” of their genetic information to pass to their offspring. Why
do the egg and sperm contain only 23 chromosomes?
Each sex cell has 23 chromosomes because when they unite, they make 46 chromosomes
which is the correct number of chromosomes for a human.
9. How are the genes and alleles alike and different?
Pairs of chromosomes carry the same genes, but each chromosome may have a different
version of the gene (allele).
10. Consider two children with the same two parents. Would you expect them to have the same set of
chromosomes? Explain why or why not.
No, each sex cell is different. Every time a sex cell is made, each allele has a 50% chance of
being part of the chromosome.
11. How many genes do humans have?
30,000 pairs
12. How are genes and chromosomes related?
Each gene is a small portion of a chromosome.
13. What is DNA?
A long molecule that makes up genes: deoxyribonucleic acid
14. In your own words, define mutation.
A mutation is when genes are copied wrong.
15. How exactly does a mutation change the form of an organism?
A mutation can show up in many ways. Sometimes they can be helpful or not affect anything
but mostly they are harmful and can cause a genetic disease.
16. When do such mutations occur?
When the chromosomes are copied to make a new set of chromosomes.