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Biology Chapter 10
Genes and Chromosomes
| Question | Answer |
|---|---|
| Where are chromosomes located? | in the nucleus |
| Where are genes located? | on chromosomes |
| What did mendel say about organisms? | that they have 2 factors for each trait except for gametes |
| Why do gametes only have one factor? | diploid cells that have 2 copies of each chromosome divide to form haploid gametes which have only 1 copy of each chromosome |
| What did mendel hypothesize about the factors? | that they would seperate when gametes are formed |
| What hapens to the homologous chromosomes in meiosis 1? | they are seperated from each other |
| What did walter sutton do? | he used microscope to study chromosomes during sperm formation in grasshoppers |
| What did walter sutton conclude about the chromosomes? | they behave in the way we would expect to see the carriers of genetic info would behave |
| What is the chromosme therory of heredity? | genes on chromosomes are linked together which means they are also inherited together |
| T-F Linked genes undergo independent assortment | F |
| How are genes located on seperate chromosomes inherited? | independently |
| What did Thomas Hunt Morgan do? | used fruit fly for genetic studies |
| What is the proper name for fruit fly? | Drosophilia melanogaster |
| What are three reasons to use the fruit fly> | small size=easy to maintence in the lab, simple genetic system of 8 chromosomes, generate new generation in a few weeks |
| What was morgans first cross? | gray flies/normal wings x black flies/small wings |
| What is the genotype of morgans first cross? | GGWW x ggww |
| What were the results of morgans first cross? | all off spring were gray/normal GGWW |
| What was morgans expected results for his first cross? | 25% for each |
| what were his actual results | GW-41.5%, Gw-7.5%, gW-7. |
| Why did morgan get the results he did in his first cross? | the genes for body color and wing size must be connected. (linked) |
| What are linkage groups? | packages of genes that are always inherited together |
| How many linkage groups are per pair of homologous chromosomes? | 1 |
| Does linkage explain all of morgans results? | no, 17% of the time he got other combinations. |
| Why? | morgan and is associate sturtevant proposed that linkages could be broken |
| How is broken linkage explained? | crossing over |
| When does crossing over occur? | meiosis 1 and produces a new combinations of genes which increase genetic variety (diversity) |
| What are recombinants? | individuals with new combinations of genes |
| when are recombinants formed? | during crossing over |
| How does crossing over occur? | randomly along linkage groups |
| What does the frequency of crossing over depend on? | the distance between genes |
| The further apart the genes.. | the more often crossing over occurs |
| crossing over is rare between what genes? | that are close together |
| What did nettie stevens do? | used meal worms |
| What did she notice about females? | they had 20 large chromosomes |
| What did nettie notice about males? | they had 19 large and 1 large chromosome |
| Was her results the same for fruit flies? | yes |
| What are sex chromosomes? | mistmatched pairs of chromosomes |
| What do sex chromosomes determine? | gender |
| What kind of chromosomes do females have? | 2 matching sex chromosomes. (XX) |
| What chromosomes do males have? | 2 different chromosomes (XY) |
| What are autosomes? | chromosomes that are the same in males and females |
| Female gametes... | contain 1 x chromosome. |
| Male gametes.. | 50% carry x, 50% carry Y |
| Who determines the sex of an offspring? | males |
| What are sex linked genes? | genes located on sex chromosomes |
| Who discovered first sex linked genes? | Thomas Hunt Morgan |
| What was morgans fruit fly experiment | white eyed male X red eyed female |
| What were the results of morgans 2nd experiment | all offspring had red eyes |
| What was the F1 Cross results? | 3:1 ratio of red eyes to white |
| What were morgans conclusion? | red is dominant over white |
| What was morgans observation? | all white eyed flies are male |
| What was morgans explanation? | eye color gene in fruit flies is located on X chromosome |
Created by:
lorelai91492
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