Sex cells have one set of chromosomes; body cells have two.
Take a look at human chromosomes.
HI! Let's look at human chromosomes. This is a photomicrograph of stained human chromosomes from one body cell. How many chromosomes are there? 92. No, count again. 23. No, try again. These are the broken pieces of one long chromosome. No, Walther Flemming did think that chromosomes exist as one long piece that broke up during mitosis, but this is not true. 46. That is correct. Human cells normally have 46 chromosomes; this is the diploid number. Chromosomes are usually arranged in a karyotype, where homologs are shown side by side. This is useful for identifying some human disorders. In this karyotype, how many pairs of chromosomes are there? 46. No, try again. 23. That is correct. [HUMAN KARYOTYPE] Humans have 23 pairs of homologous chromosomes. How many of these chromosomes will be found in an egg cell? All 46 chromosomes. No, sex cells have a half set of chromosomes. 23, one from each pair. That is correct. 23, pairs 1-11 and one selected randomly from the remaining pairs. Human sex cells do have 23 chromosomes, but not these 23. 23, 11 random pairs and one extra. Human sex cells do have 23 chromosomes, but not these 23. None, egg cells don't have chromosomes. No, sex cells do have chromosomes. Meiosis reduces chromosome number so that sex cells (eggs and sperm) have a half set of chromosomesâ€“one homolog of each pair. This is the haploid number. CONGRATULATIONS! YOU'RE SO SMART!
walther flemming, human karyotype, human chromosomes, egg cells, sex cells, haploid number, diploid number, photomicrograph, homolog, mitosis, body cell, homologs, homologous chromosomes, meiosis
- ID: 16248
- Source: DNALC.DNAFTB
Offspring arise from the union of specialized sex cells â a female egg and a male sperm.
DNAFTB Animation 8: Theodor Boveri presents chromosomes' role in development.
Study of meiosis revealed the chromosomal basis of gender.
In 1882, Walther Flemming published the definitive study of the cellular process of mitosis.
Theodor Boveri described the process of meiosis. He also showed that although chromosomes may look similar, they have specific hereditary qualities.
DNAFTB Animation 9:Nettie Stevens and Edmund Wilson explain how gender is determined by special chromosomes.
Model organisms share with humans many key biochemical and physiological functions that have been conserved (maintained) by evolution.
DNAFTB Problem 7:Look at the chromosome number of fruit flies.
Yeast was the first eukaryote organism to have its entire genome sequenced. It has remained at the forefront of genetics research because it is quick and easy to grow.
DNAFTB Animation 7: Walther Flemming explains the phases of mitosis.