Genetics: Chromosomes Flashcards
While cell division in plants and algae was observed in the 1830s, why was cell division in animal cells only observed in 1873?
They were harder to grow in cultures, leading difficulties to getting good samples
The germ plasm theory states that we have 2 types of cells. What are they?
Somatic (liver, brain, etc) and germ (reproductive) cells
in homologous chromosomes,
traits line up
What is genetic drift?
Mutations dying because of random events
What is the process of cell division called?
Mitosis
What was the process of discovering nucleic acides?
1860s - Isolated phosphorous rich chemicals from leukocytes. Named nuclein, because they were isolated from the nuclei of the cells
1880s - Renamed nucleic acid because of their acidic nature
1890s - Isolated 5 distinct nucleotide bases: Adenine, guanine, cytosine, thymine (for DNA), and uracil (for RNA)
When and who identified chromatins to be the threadlike structures in nuclei?
1880s - Walther Flemming
Who first used the term chromosome?
1888 - Waldeyer- Hartz
When do nuclear chromosomes become visible?
When they are condensed
What occurs during mitosis?
Replicated chromosomes are separated into two new nuclei during the process of cell division
Cells undergo ____ _______ as the organism grows, and also to replace damaged cells.
Dividing cells undergo ______ to allocate chromosomes to each daughter cell
cell division, mitosis
What is germ plasma theory? When and who proposed it?
Inheritance in multicellular organisms takes place via the germ cells in the gonads such as egg cells and sperm cells (gametes). Other cells (somatic cells) are not the agents of heredity.
1892, August Weismann
In germ plasma theory, what is germplasm?
The essential element of germ cells that is passed from one generation to the next
In eukaryotic cells, where can DNA be stored?
nuclear chromosomes, mitochondria, and chloroplasts
When and who developed parts o the chromosome theory of inheritance? What did their work show?
1902, Walter Sutton and Theodor Boveri
Chromosomes are seen in all dividing cells and pass from generation to the next. Stated that chromosomes might be the basis of genetic inheritance, but was controversial at the time
Scientists first thought that _______ carried the genetic material. Why?
Proteins
It was known that chromosomes also contained proteins. They though the structure of DNA was too simple to give rise to the traits, unlike proteins with over 20 amino acids
What is the basic building block of DNA?
phosphate, sugar (deoxyribose), and 4 bases (AGCT)
Which two bases are purines?
Adenine and guanine
Which two bases are pyrimidines?
Cytosine and thymine
What is the length of DNA from the largest human chromosome?
10 cm (250*10^6 base pairs)
Early scientists incorrectly insisted that DNA was probably only __ nucleotides long and that the amounts of the four bases were the same in all DNA molecules
10
When and who conducted Experiment 1? What was the conclusion?
1928, Frederick Griffith.
He discovered that bacteria are capable of transferring genetic information though a process called transformation
Describe the process of Experiment 1
Griffith was trying to make a vaccine for pneumonia with the bacteria.
He experimented with 2 strains: Rough and Smooth.
Only Smooth was virulent, causing pneumonia and death in mice
He then showed the heat-killed Smooth were no longer virulent
However, if he mixed the dead Smooth with live Rough, the Rough transformed into Smooth bacteria
This meant dead Smooth could still transfer genetic material into Rough
When and who conducted Experiment 2? What was the conclusion?
1944, Avery, Macleod, and McCarty
They discovered that DNA likely caused the bacterial transformation reported in Griffiths experiment
Describe the process of Experiment 2
Tried to explain the transformation factor in heat killed Smooth bacteria
They took 5 instances of dead Smooth and then destroyed specific macro molecules (sugars, proteins, lipids, RNA, and DNA)
Each batch was mixed with live R and injected into mice
All mice died except for the one with destroyed DNA. Live Smooth were recovered only from the dead mice. In the dead mice, the Rough had transformed into the virulent Smooth, which killed them.
Suggested that the transforming factor was likely DNA
However, they did not disprove that another unknown substance was the transforming agent
When and who conducted Experiment 3? What was the conclusion?
1952, Hershey and Chase
Provided evidence that DNA was responsible for transforming bacteria, not proteins
Describe the process of Experiment 3
They knew bacteriophages could inject some substance (DNA or protein) into bacteria. The substance transformed host bacteria, making them make more phages
They made 2 batches of phages, one with radioactive DNA and the other radioactive proteins
Each batch was made to infect bacteria
After infection, each culture was blended and centrifuged to separate bacteria from phage debris. Bacteria remain at bottom and phage parts remain at top
Radioactivity was then measured in bottom and top.
Radioactive stuff was found in the bacteria for DNA
Radioactive stuff was found in the phage parts for protein
TLDR; DNA is genetic material
What did the Sutton-Boveri chromosome theory of inheritance suggest?
Chromosomes are linear structures with genes located at specific loci along the chromosome
Humans are ______ organisms. What does that mean?
Diploid
We have 2 homologous chromosomes
What is ploidy?
The number of complete sets of chromosomes in a cell
Human gametes are _______, while all other cells are diploid
haploid
The number of chromosomes and ______ are not correlated
genes
What does the Hardy-Weinberg law predict?
That allele frequencies in a population do not change from generation to generation without evolutionary influences. (But rare mutations can be lost to genetic drift)
It measures whether a population is evolving or not
Some quantitative characteristics are caused by _________ (_______) inheritance
multigene, polygeneic
