Chromosomes

1. What are chromosomes?

Packaged DNA molecules.

2. What is chromatin?

DNA together with associated proteins in the nucleus.

3. How is DNA packaged into chromosomes?

Packaging is hierarchical: DNA forms nucleosomes then higher-order fibers looping and coiling.

4. What is a nucleosome?

A unit of DNA wrapped around histone proteins; part of the approximately 11-nm fiber.

5. What is the 30-nm fiber?

A higher level of chromatin packaging described in the notes.

6. Is chromosome packaging static or dynamic?

Dynamic; it changes during the cell cycle and along the length of a chromosome.

7. What is euchromatin?

Less-condensed chromatin.

8. What is heterochromatin?

More-condensed chromatin.

9. When are chromosomes usually easiest to visualize?

During metaphase of mitosis when they are condensed.

10. What is a replicated chromosome?

A chromosome copied during DNA replication and consisting of two sister chromatids.

11. What are sister chromatids?

The two copies of a replicated chromosome joined together.

12. What process creates sister chromatids?

DNA replication.

13. What is a non-replicated chromosome?

A chromosome consisting of one DNA molecule

14. What is the centromere?

A chromosome region important for joining sister chromatids and organizing chromosome movement.

15. What is the kinetochore?

A protein structure associated with the centromere where spindle fibers attach.

16. What do spindle fibers do?

They attach to kinetochores and help move chromosomes during mitosis.

17. What are telomeres?

Protective chromosome-end regions.

18. What is a metacentric chromosome?

A chromosome with a centromere approximately in the middle.

19. What is a submetacentric chromosome?

A chromosome with a centromere somewhat off-center.

20. What is an acrocentric chromosome?

A chromosome with a centromere close to one end.

21. What is a telocentric chromosome?

A chromosome with a centromere at or extremely close to one end.

22. What is a karyotype?

An organized display of chromosomes

23. How are karyotypes made?

Chromosomes are captured

24. What are homologous chromosomes?

A pair of chromosomes with the same general genes and corresponding loci; one is inherited from each parent.

25. What are non-homologous chromosomes?

Chromosomes that are not a matching homologous pair.

26. Where does each chromosome in a homologous pair come from?

One comes from the mother and one comes from the father.

27. What are autosomes?

Chromosomes that are not sex chromosomes.

28. What are sex chromosomes?

Chromosomes involved in sex determination in some species such as X and Y or Z and W.

29. Do all species have different chromosomes in males and females?

No. Whether sex chromosomes differ between sexes depends on the species.

30. What is a locus?

The physical location of a gene or DNA sequence on a chromosome.

31. What is an allele?

A version of a gene or DNA sequence that can differ from another version.

32. What is an SNP?

A single-nucleotide polymorphism; variation involving one DNA base.

33. What is an indel?

An insertion or deletion of DNA bases.

34. How are new alleles created?

Through changes in DNA sequence

35. What is a genotype?

The allele combination an individual has.

36. What does homozygous mean?

Having two identical alleles at a locus.

37. What does heterozygous mean?

Having two different alleles at a locus.

38. What is ploidy?

The number of complete sets of chromosomes in a cell.

39. What is haploid?

Having one set of chromosomes

40. What is diploid?

Having two sets of chromosomes represented as 2n.

41. What is polyploid?

Having more than two complete sets of chromosomes.

42. What does n represent?

The haploid chromosome number.

43. What does 2n represent?

The diploid chromosome number.

Can chromosome number, size, and shape evolve?

Yes; chromosome structure and number can change over evolutionary time.