Download Differentiation in Germline Cells

Differentiation in Germline Cells
Higher Human Biology
Unit 1 – Sub-Topic 1 (c)
Learning Outcomes
o The nucleus of a germline cell can divide by
mitosis to produce more germline cells or divide
by meiosis to produce haploid gametes.
o Mutations that occur in germline cells will be
passed to offspring whereas mutations in somatic
cells will not.
Germline cells
Germline cells include the gametes and the cells that produce the
gametes.
Division of germline cells
• Germline cells are diploid
(23pairs of homologous
chromosomes).
• Germline cells can divide
by mitosis to produce
more germline cells.
• Gamete mother cells
divide by meiosis to
produce gametes.
Mutations
• Mutations in germline cells are passed onto
offspring.
– For example: Cystic Fibrosis
• A gene mutation on chromosome 7 may become the recessive
form (leading to production of thick and sticky mucus). This
mutant allele is passed onto gametes during meiosis. If the
other parent is a carrier of the same recessive allele then the
resulting zygote will be a cystic fibrosis sufferer.
• A mutation in a somatic cell, even if it leads to a
phenotypic change, is not passed onto offspring.
Questions
1. What is the difference between the terms
haploid and diploid?
2. What is a germline cell?
3. Describe how a diploid germline cell produces
haploid gametes.
4. In which type of cell (somatic or germline) is a
mutation not passed on to the members of the
next generation?
Answers
1. Haploid means a single set of 23 chromosomes.
Diploid is a double set of chromosomes – 46
Chromosomes arranged as 23 pairs.
2. Germline cell is a cell that will eventually lead to
the formation of sex cells (gametes).
3. By a form of nuclear division called Meiosis. The
genetic material is doubled then it is divided
between 4 nuclei. Each receives a set of 23
single chromosomes.
4. Mutations in Germline cells are passed onto
members of the next generation.